diff --git a/.coveragerc b/.coveragerc
new file mode 100644
index 0000000..88fdb9d
--- /dev/null
+++ b/.coveragerc
@@ -0,0 +1,21 @@
+[report]
+exclude_lines =
+    pragma: no cover
+    def __repr__
+    def __str__
+    if self.debug:
+    if settings.DEBUG
+    raise AssertionError
+    raise NotImplementedError
+    if 0:
+    if __name__ == .__main__.:
+
+omit =
+    BUILD
+    anvil/test.py
+    run-tests.py
+    *_test.py
+    /usr/**
+    /tmp/**
+    /Library/Python/**
+    /private/var/**
diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..edb2a4d
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,66 @@
+# ==============================================================================
+# Misc system junk
+# ==============================================================================
+
+.DS_Store
+._*
+.Spotlight-V100
+.Trashes
+.com.apple.*
+Thumbs.db
+Desktop.ini
+
+# ==============================================================================
+# Projects/IDE files
+# ==============================================================================
+
+# Sublime Text
+*.sublime-project
+*.sublime-workspace
+
+# VIM
+.*.sw[a-z]
+*.un~
+Session.vim
+
+# TextMate
+*.tmproj
+*.tmproject
+tmtags
+
+# Eclipse
+.project
+.metadata
+
+# ==============================================================================
+# Temp generated code
+# ==============================================================================
+
+*.py[co]
+.coverage
+
+# ==============================================================================
+# Logs and dumps
+# ==============================================================================
+
+npm-debug.log
+
+# ==============================================================================
+# Build system output
+# ==============================================================================
+
+# Python
+*.egg-info
+
+# npm/node
+.lock-wscript
+node_modules/**/build/
+node_modules/.bin/
+
+# coverage/etc
+scratch/
+
+.build-cache/
+build-out/
+build-gen/
+build-bin/
diff --git a/anvil/__init__.py b/anvil/__init__.py
new file mode 100644
index 0000000..7b692e2
--- /dev/null
+++ b/anvil/__init__.py
@@ -0,0 +1,6 @@
+# Copyright 2012 Google Inc. All Rights Reserved.
+
+"""
+"""
+
+__author__ = 'benvanik@google.com (Ben Vanik)'
diff --git a/anvil/async.py b/anvil/async.py
new file mode 100644
index 0000000..f60d6f7
--- /dev/null
+++ b/anvil/async.py
@@ -0,0 +1,154 @@
+# Copyright 2012 Google Inc. All Rights Reserved.
+
+__author__ = 'benvanik@google.com (Ben Vanik)'
+
+
+class Deferred(object):
+  """A simple deferred object, designed for single-threaded tracking of futures.
+  """
+
+  def __init__(self):
+    """Initializes a deferred."""
+    self._callbacks = []
+    self._errbacks = []
+    self._is_done = False
+    self._failed = False
+    self._exception = None
+    self._args = None
+    self._kwargs = None
+
+  def is_done(self):
+    """Whether the deferred has completed (either succeeded or failed).
+
+    Returns:
+      True if the deferred has completed.
+    """
+    return self._is_done
+
+  def add_callback_fn(self, fn):
+    """Adds a function that will be called when the deferred completes
+    successfully.
+
+    The arguments passed to the function will be those arguments passed to
+    callback. If multiple callbacks are registered they will all be called with
+    the same arguments, so don't modify them.
+
+    If the deferred has already completed when this function is called then the
+    callback will be made immediately.
+
+    Args:
+      fn: Function to call back.
+    """
+    if self._is_done:
+      if not self._failed:
+        fn(*self._args, **self._kwargs)
+      return
+    self._callbacks.append(fn)
+
+  def add_errback_fn(self, fn):
+    """Adds a function that will be called when the deferred completes with
+    an error.
+
+    The arguments passed to the function will be those arguments passed to
+    errback. If multiple callbacks are registered they will all be called with
+    the same arguments, so don't modify them.
+
+    If the deferred has already completed when this function is called then the
+    callback will be made immediately.
+
+    Args:
+      fn: Function to call back.
+    """
+    if self._is_done:
+      if self._failed:
+        fn(*self._args, **self._kwargs)
+      return
+    self._errbacks.append(fn)
+
+  def callback(self, *args, **kwargs):
+    """Completes a deferred successfully and calls any registered callbacks."""
+    assert not self._is_done
+    self._is_done = True
+    self._args = args
+    self._kwargs = kwargs
+    callbacks = self._callbacks
+    self._callbacks = []
+    self._errbacks = []
+    for fn in callbacks:
+      fn(*args, **kwargs)
+
+  def errback(self, *args, **kwargs):
+    """Completes a deferred with an error and calls any registered errbacks."""
+    assert not self._is_done
+    self._is_done = True
+    self._failed = True
+    if len(args) and isinstance(args[0], Exception):
+      self._exception = args[0]
+    self._args = args
+    self._kwargs = kwargs
+    errbacks = self._errbacks
+    self._callbacks = []
+    self._errbacks = []
+    for fn in errbacks:
+      fn(*args, **kwargs)
+
+
+def gather_deferreds(deferreds, errback_if_any_fail=False):
+  """Waits until all of the given deferreds callback.
+  Once all have completed this deferred will issue a callback
+  with a list corresponding to each waiter, with a (success, args, kwargs)
+  tuple for each deferred.
+
+  The deferred returned by this will only ever issue callbacks, never errbacks.
+
+  Args:
+    deferreds: A list of deferreds to wait on.
+    errback_if_any_fail: True to use errback instead of callback if at least one
+        of the input deferreds fails.
+
+  Returns:
+    A deferred that is called back with a list of tuples corresponding to each
+    input deferred. The tuples are of (success, args, kwargs) with success
+    being a boolean True if the deferred used callback and False if it used
+    errback.
+  """
+  if isinstance(deferreds, Deferred):
+    deferreds = [deferreds]
+  gather_deferred = Deferred()
+  deferred_len = len(deferreds)
+  if not deferred_len:
+    gather_deferred.callback([])
+    return gather_deferred
+
+  pending = [deferred_len]
+  result_tuples = deferred_len * [None]
+  def _complete():
+    pending[0] -= 1
+    if not pending[0]:
+      if not errback_if_any_fail:
+        gather_deferred.callback(result_tuples)
+      else:
+        any_failed = False
+        for result in result_tuples:
+          if not result[0]:
+            any_failed = True
+            break
+        if any_failed:
+          gather_deferred.errback(result_tuples)
+        else:
+          gather_deferred.callback(result_tuples)
+
+  def _makecapture(n, deferred):
+    def _callback(*args, **kwargs):
+      result_tuples[n] = (True, args, kwargs)
+      _complete()
+    def _errback(*args, **kwargs):
+      result_tuples[n] = (False, args, kwargs)
+      _complete()
+    deferred.add_callback_fn(_callback)
+    deferred.add_errback_fn(_errback)
+
+  for n in xrange(deferred_len):
+    _makecapture(n, deferreds[n])
+
+  return gather_deferred
diff --git a/anvil/async_test.py b/anvil/async_test.py
new file mode 100755
index 0000000..f1efa0c
--- /dev/null
+++ b/anvil/async_test.py
@@ -0,0 +1,293 @@
+#!/usr/bin/python
+
+# Copyright 2012 Google Inc. All Rights Reserved.
+
+"""Tests for the async module.
+"""
+
+__author__ = 'benvanik@google.com (Ben Vanik)'
+
+
+import unittest2
+
+from async import Deferred, gather_deferreds
+from test import AsyncTestCase
+
+
+class DeferredTest(unittest2.TestCase):
+  """Behavioral tests of the Deferred type."""
+
+  def testMultiCall(self):
+    d = Deferred()
+    d.callback()
+    with self.assertRaises(AssertionError):
+      d.callback()
+    d = Deferred()
+    d.errback()
+    with self.assertRaises(AssertionError):
+      d.errback()
+    d = Deferred()
+    d.callback()
+    with self.assertRaises(AssertionError):
+      d.errback()
+    d = Deferred()
+    d.errback()
+    with self.assertRaises(AssertionError):
+      d.callback()
+
+  def testCallbackArgs(self):
+    cb = {}
+    def cb_thunk(*args, **kwargs):
+      cb['done'] = True
+      cb['args'] = args
+      cb['kwargs'] = kwargs
+
+    d = Deferred()
+    self.assertFalse(d.is_done())
+    d.callback()
+    self.assertTrue(d.is_done())
+
+    d = Deferred()
+    self.assertFalse(d.is_done())
+    d.errback()
+    self.assertTrue(d.is_done())
+
+    d = Deferred()
+    d.add_callback_fn(cb_thunk)
+    d.callback()
+    self.assertNotEqual(len(cb), 0)
+    self.assertTrue(cb['done'])
+    self.assertEqual(len(cb['args']), 0)
+    self.assertEqual(len(cb['kwargs']), 0)
+    cb.clear()
+
+    d = Deferred()
+    d.add_callback_fn(cb_thunk)
+    d.callback('a', 'b')
+    self.assertNotEqual(len(cb), 0)
+    self.assertTrue(cb['done'])
+    self.assertEqual(len(cb['args']), 2)
+    self.assertEqual(cb['args'][0], 'a')
+    self.assertEqual(cb['args'][1], 'b')
+    self.assertEqual(len(cb['kwargs']), 0)
+    cb.clear()
+
+    d = Deferred()
+    d.add_callback_fn(cb_thunk)
+    d.callback('a', b='b')
+    self.assertNotEqual(len(cb), 0)
+    self.assertTrue(cb['done'])
+    self.assertEqual(len(cb['args']), 1)
+    self.assertEqual(cb['args'][0], 'a')
+    self.assertEqual(len(cb['kwargs']), 1)
+    self.assertEqual(cb['kwargs']['b'], 'b')
+    cb.clear()
+
+  def testCallbackOrder(self):
+    cb = {}
+    def cb_thunk(*args, **kwargs):
+      cb['done'] = True
+      cb['args'] = args
+      cb['kwargs'] = kwargs
+
+    d = Deferred()
+    d.add_callback_fn(cb_thunk)
+    d.callback('a')
+    self.assertNotEqual(len(cb), 0)
+    self.assertTrue(cb['done'])
+    self.assertEqual(len(cb['args']), 1)
+    self.assertEqual(cb['args'][0], 'a')
+    self.assertEqual(len(cb['kwargs']), 0)
+    cb.clear()
+
+    d = Deferred()
+    d.callback('a')
+    d.add_callback_fn(cb_thunk)
+    self.assertNotEqual(len(cb), 0)
+    self.assertTrue(cb['done'])
+    self.assertEqual(len(cb['args']), 1)
+    self.assertEqual(cb['args'][0], 'a')
+    self.assertEqual(len(cb['kwargs']), 0)
+    cb.clear()
+
+    d = Deferred()
+    d.add_errback_fn(cb_thunk)
+    d.errback('a')
+    self.assertNotEqual(len(cb), 0)
+    self.assertTrue(cb['done'])
+    self.assertEqual(len(cb['args']), 1)
+    self.assertEqual(cb['args'][0], 'a')
+    self.assertEqual(len(cb['kwargs']), 0)
+    cb.clear()
+
+    d = Deferred()
+    d.errback('a')
+    d.add_errback_fn(cb_thunk)
+    self.assertNotEqual(len(cb), 0)
+    self.assertTrue(cb['done'])
+    self.assertEqual(len(cb['args']), 1)
+    self.assertEqual(cb['args'][0], 'a')
+    self.assertEqual(len(cb['kwargs']), 0)
+    cb.clear()
+
+    d = Deferred()
+    d.add_callback_fn(cb_thunk)
+    d.errback('a')
+    self.assertEqual(len(cb), 0)
+    cb.clear()
+
+    d = Deferred()
+    d.errback('a')
+    d.add_callback_fn(cb_thunk)
+    self.assertEqual(len(cb), 0)
+    cb.clear()
+
+    d = Deferred()
+    d.add_errback_fn(cb_thunk)
+    d.callback('a')
+    self.assertEqual(len(cb), 0)
+    cb.clear()
+
+    d = Deferred()
+    d.callback('a')
+    d.add_errback_fn(cb_thunk)
+    self.assertEqual(len(cb), 0)
+    cb.clear()
+
+  def testMultiCallbacks(self):
+    cbs = []
+    def cb_multi_thunk(*args, **kwargs):
+      cbs.append({
+          'done': True,
+          'args': args,
+          'kwargs': kwargs
+          })
+
+    d = Deferred()
+    d.add_callback_fn(cb_multi_thunk)
+    d.callback('a')
+    self.assertEqual(len(cbs), 1)
+    self.assertNotEqual(len(cbs[0]), 0)
+    self.assertEqual(cbs[0]['args'][0], 'a')
+    cbs[:] = []
+
+    d = Deferred()
+    d.add_callback_fn(cb_multi_thunk)
+    d.add_callback_fn(cb_multi_thunk)
+    d.callback('a')
+    self.assertEqual(len(cbs), 2)
+    self.assertNotEqual(len(cbs[0]), 0)
+    self.assertNotEqual(len(cbs[1]), 0)
+    self.assertEqual(cbs[0]['args'][0], 'a')
+    self.assertEqual(cbs[1]['args'][0], 'a')
+    cbs[:] = []
+
+    d = Deferred()
+    d.add_callback_fn(cb_multi_thunk)
+    d.callback('a')
+    d.add_callback_fn(cb_multi_thunk)
+    self.assertEqual(len(cbs), 2)
+    self.assertNotEqual(len(cbs[0]), 0)
+    self.assertNotEqual(len(cbs[1]), 0)
+    self.assertEqual(cbs[0]['args'][0], 'a')
+    self.assertEqual(cbs[1]['args'][0], 'a')
+    cbs[:] = []
+
+    d = Deferred()
+    d.callback('a')
+    d.add_callback_fn(cb_multi_thunk)
+    d.add_callback_fn(cb_multi_thunk)
+    self.assertEqual(len(cbs), 2)
+    self.assertNotEqual(len(cbs[0]), 0)
+    self.assertNotEqual(len(cbs[1]), 0)
+    self.assertEqual(cbs[0]['args'][0], 'a')
+    self.assertEqual(cbs[1]['args'][0], 'a')
+    cbs[:] = []
+
+
+class GatherTest(AsyncTestCase):
+  """Behavioral tests for the async gather function."""
+
+  def testGather(self):
+    d = gather_deferreds([])
+    self.assertCallbackEqual(d, [])
+
+    da = Deferred()
+    db = Deferred()
+    dc = Deferred()
+    df = Deferred()
+    d = gather_deferreds([da, db, dc, df])
+    df.errback()
+    dc.callback('c')
+    db.callback('b')
+    da.callback('a')
+    self.assertCallbackEqual(d, [
+        (True, ('a',), {}),
+        (True, ('b',), {}),
+        (True, ('c',), {}),
+        (False, (), {})])
+
+    da = Deferred()
+    db = Deferred()
+    dc = Deferred()
+    df = Deferred()
+    df.errback('f')
+    dc.callback('c')
+    d = gather_deferreds([da, db, dc, df])
+    db.callback('b')
+    da.callback('a')
+    self.assertCallbackEqual(d, [
+        (True, ('a',), {}),
+        (True, ('b',), {}),
+        (True, ('c',), {}),
+        (False, ('f',), {})])
+
+  def testErrback(self):
+    d = gather_deferreds([], errback_if_any_fail=True)
+    self.assertCallbackEqual(d, [])
+
+    da = Deferred()
+    db = Deferred()
+    dc = Deferred()
+    d = gather_deferreds([da, db, dc], errback_if_any_fail=True)
+    dc.callback('c')
+    db.callback('b')
+    da.callback('a')
+    self.assertCallbackEqual(d, [
+        (True, ('a',), {}),
+        (True, ('b',), {}),
+        (True, ('c',), {})])
+
+    da = Deferred()
+    db = Deferred()
+    dc = Deferred()
+    df = Deferred()
+    d = gather_deferreds([da, db, dc, df], errback_if_any_fail=True)
+    df.errback()
+    dc.callback('c')
+    db.callback('b')
+    da.callback('a')
+    self.assertErrbackEqual(d, [
+        (True, ('a',), {}),
+        (True, ('b',), {}),
+        (True, ('c',), {}),
+        (False, (), {})])
+
+    da = Deferred()
+    db = Deferred()
+    dc = Deferred()
+    df = Deferred()
+    df.errback('f')
+    dc.callback('c')
+    d = gather_deferreds([da, db, dc, df], errback_if_any_fail=True)
+    db.callback('b')
+    da.callback('a')
+    self.assertErrbackEqual(d, [
+        (True, ('a',), {}),
+        (True, ('b',), {}),
+        (True, ('c',), {}),
+        (False, ('f',), {})])
+
+
+if __name__ == '__main__':
+  unittest2.main()
diff --git a/anvil/commands/__init__.py b/anvil/commands/__init__.py
new file mode 100644
index 0000000..7b692e2
--- /dev/null
+++ b/anvil/commands/__init__.py
@@ -0,0 +1,6 @@
+# Copyright 2012 Google Inc. All Rights Reserved.
+
+"""
+"""
+
+__author__ = 'benvanik@google.com (Ben Vanik)'
diff --git a/anvil/commands/build_command.py b/anvil/commands/build_command.py
new file mode 100644
index 0000000..90cd556
--- /dev/null
+++ b/anvil/commands/build_command.py
@@ -0,0 +1,52 @@
+# Copyright 2012 Google Inc. All Rights Reserved.
+
+"""Builds a set of target rules.
+
+Examples:
+# Build the given rules
+manage.py build :some_rule some/path:another_rule
+# Force a full rebuild (essentially a 'manage.py clean')
+manage.py build --rebuild :some_rule
+"""
+
+__author__ = 'benvanik@google.com (Ben Vanik)'
+
+
+import argparse
+
+import anvil.commands.util as commandutil
+from anvil.manage import manage_command
+
+
+def _get_options_parser():
+  """Gets an options parser for the given args."""
+  parser = commandutil.create_argument_parser('manage.py build', __doc__)
+
+  # Add all common args
+  commandutil.add_common_build_args(parser, targets=True)
+
+  # 'build' specific
+  parser.add_argument('--rebuild',
+                      dest='rebuild',
+                      action='store_true',
+                      default=False,
+                      help=('Cleans all output and caches before building.'))
+
+  return parser
+
+
+@manage_command('build', 'Builds target rules.')
+def build(args, cwd):
+  parser = _get_options_parser()
+  parsed_args = parser.parse_args(args)
+
+  # Handle --rebuild
+  if parsed_args.rebuild:
+    if not commandutil.clean_output(cwd):
+      return False
+
+  (result, all_target_outputs) = commandutil.run_build(cwd, parsed_args)
+
+  print all_target_outputs
+
+  return result
diff --git a/anvil/commands/clean_command.py b/anvil/commands/clean_command.py
new file mode 100644
index 0000000..563037b
--- /dev/null
+++ b/anvil/commands/clean_command.py
@@ -0,0 +1,33 @@
+# Copyright 2012 Google Inc. All Rights Reserved.
+
+"""Cleans all build-* paths and caches.
+Attempts to delete all paths the build system creates.
+"""
+
+__author__ = 'benvanik@google.com (Ben Vanik)'
+
+
+import argparse
+import os
+import shutil
+import sys
+
+import anvil.commands.util as commandutil
+from anvil.manage import manage_command
+
+
+def _get_options_parser():
+  """Gets an options parser for the given args."""
+  parser = commandutil.create_argument_parser('manage.py clean', __doc__)
+
+  # 'clean' specific
+
+  return parser
+
+
+@manage_command('clean', 'Cleans outputs and caches.')
+def clean(args, cwd):
+  parser = _get_options_parser()
+  parsed_args = parser.parse_args(args)
+
+  return commandutil.clean_output(cwd)
diff --git a/anvil/commands/deploy_command.py b/anvil/commands/deploy_command.py
new file mode 100644
index 0000000..66d12bb
--- /dev/null
+++ b/anvil/commands/deploy_command.py
@@ -0,0 +1,95 @@
+# Copyright 2012 Google Inc. All Rights Reserved.
+
+"""Runs a build and copies all output results of the specified rules to a path.
+All of the output files of the specified rules will be copied to the target
+output path. The directory structure will be exactly that of under the
+various build-*/ folders but collapsed into one.
+
+A typical deploy rule will bring together many result srcs, for example
+converted audio files or compiled code, for a specific configuration.
+One could have many such rules to target different configurations, such as
+unoptimized/uncompiled vs. optimized/packed.
+
+Examples:
+# Copy all output files of :release_all to /some/bin/, merging the output
+manage.py deploy --output=/some/bin/ :release_all
+# Clean (aka delete) /some/bin/ before doing the copy
+manage.py deploy --clean --output=/some/bin/ :release_all
+"""
+
+__author__ = 'benvanik@google.com (Ben Vanik)'
+
+
+import argparse
+import os
+import shutil
+import sys
+
+import anvil.commands.util as commandutil
+from anvil.manage import manage_command
+
+
+def _get_options_parser():
+  """Gets an options parser for the given args."""
+  parser = commandutil.create_argument_parser('manage.py deploy', __doc__)
+
+  # Add all common args
+  commandutil.add_common_build_args(parser, targets=True)
+
+  # 'deploy' specific
+  parser.add_argument('-o', '--output',
+                      dest='output',
+                      required=True,
+                      help=('Output path to place all results. Will be created '
+                            ' if it does not exist.'))
+  parser.add_argument('-c', '--clean',
+                      dest='clean',
+                      action='store_true',
+                      help=('Whether to remove all output files before '
+                            'deploying.'))
+
+  return parser
+
+
+@manage_command('deploy', 'Builds and copies output to a target path.')
+def deploy(args, cwd):
+  parser = _get_options_parser()
+  parsed_args = parser.parse_args(args)
+
+  # Build everything first
+  (result, all_target_outputs) = commandutil.run_build(cwd, parsed_args)
+  if not result:
+    # Failed - don't copy anything
+    return False
+
+  # Delete output, if desired
+  if parsed_args.clean:
+    shutil.rmtree(parsed_args.output)
+
+  # Ensure output exists
+  if not os.path.isdir(parsed_args.output):
+    os.makedirs(parsed_args.output)
+
+  # Copy results
+  for target_output in all_target_outputs:
+    # Get path relative to root
+    # This will contain the build-out/ etc
+    rel_path = os.path.relpath(target_output, cwd)
+
+    # Strip the build-*/
+    rel_path = os.path.join(*(rel_path.split(os.sep)[1:]))
+
+    # Make output path
+    deploy_path = os.path.normpath(os.path.join(parsed_args.output, rel_path))
+
+    # Ensure directory exists
+    # TODO(benvanik): cache whether we have checked yet to reduce OS cost
+    deploy_dir = os.path.dirname(deploy_path)
+    if not os.path.isdir(deploy_dir):
+      os.makedirs(deploy_dir)
+
+    # Copy!
+    print '%s -> %s' % (target_output, deploy_path)
+    shutil.copy2(target_output, deploy_path)
+
+  return result
diff --git a/anvil/commands/serve_command.py b/anvil/commands/serve_command.py
new file mode 100644
index 0000000..c09a525
--- /dev/null
+++ b/anvil/commands/serve_command.py
@@ -0,0 +1,59 @@
+# Copyright 2012 Google Inc. All Rights Reserved.
+
+"""Launches an HTTP server and optionally a continuous build daemon.
+This serves the current working directory over HTTP, similar to Python's
+SimpleHTTPServer.
+
+If a daemon port and any rules are defined then changes to the
+specified paths will automatically trigger builds. A WebSocket port is specified
+that clients can connect to and get lists of file change sets.
+
+Daemon rules should be of the form:
+file_set('some_daemon',
+         srcs=['watch_path_1/', 'watch_path_2/'],
+         deps=[':root_build_target'])
+Where the given srcs will be recursively watched for changes to trigger the
+rules specified in deps.
+
+Examples:
+# Simple HTTP server
+manage.py serve
+manage.py serve --http_port=8080
+# HTTP server + build daemon
+manage.py serve :some_daemon
+manage.py serve --http_port=8080 --daemon_port=8081 :some_daemon
+"""
+
+__author__ = 'benvanik@google.com (Ben Vanik)'
+
+
+import argparse
+import os
+import sys
+
+import anvil.commands.util as commandutil
+from anvil.manage import manage_command
+
+
+def _get_options_parser():
+  """Gets an options parser for the given args."""
+  parser = commandutil.create_argument_parser('manage.py serve', __doc__)
+
+  # Add all common args
+  commandutil.add_common_build_args(parser, targets=True)
+
+  # 'serve' specific
+
+  return parser
+
+
+@manage_command('serve', 'Continuously builds and serves targets.')
+def serve(args, cwd):
+  parser = _get_options_parser()
+  parsed_args = parser.parse_args(args)
+
+  (result, all_target_outputs) = commandutil.run_build(cwd, parsed_args)
+
+  print all_target_outputs
+
+  return result
diff --git a/anvil/commands/test_command.py b/anvil/commands/test_command.py
new file mode 100644
index 0000000..7cef22f
--- /dev/null
+++ b/anvil/commands/test_command.py
@@ -0,0 +1,43 @@
+# Copyright 2012 Google Inc. All Rights Reserved.
+
+"""Builds and executes a set of test rules.
+TODO: need some custom rules (test_js or something?) that provide parameters
+      to some test framework (BusterJS?)
+
+Example:
+manage.py test :test_rule ...
+"""
+
+__author__ = 'benvanik@google.com (Ben Vanik)'
+
+
+import argparse
+import os
+import sys
+
+import anvil.commands.util as commandutil
+from anvil.manage import manage_command
+
+
+def _get_options_parser():
+  """Gets an options parser for the given args."""
+  parser = commandutil.create_argument_parser('manage.py test', __doc__)
+
+  # Add all common args
+  commandutil.add_common_build_args(parser, targets=True)
+
+  # 'test' specific
+
+  return parser
+
+
+@manage_command('test', 'Builds and runs test rules.')
+def test(args, cwd):
+  parser = _get_options_parser()
+  parsed_args = parser.parse_args(args)
+
+  (result, all_target_outputs) = commandutil.run_build(cwd, parsed_args)
+
+  print all_target_outputs
+
+  return result
diff --git a/anvil/commands/util.py b/anvil/commands/util.py
new file mode 100644
index 0000000..b912ed9
--- /dev/null
+++ b/anvil/commands/util.py
@@ -0,0 +1,152 @@
+# Copyright 2012 Google Inc. All Rights Reserved.
+
+"""Common command utilities.
+"""
+
+__author__ = 'benvanik@google.com (Ben Vanik)'
+
+
+import argparse
+import os
+import shutil
+
+from anvil.context import BuildEnvironment, BuildContext
+from anvil.project import FileModuleResolver, Project
+from anvil.task import InProcessTaskExecutor, MultiProcessTaskExecutor
+
+
+# Hack to get formatting in usage() correct
+class _ComboHelpFormatter(argparse.RawDescriptionHelpFormatter,
+                          argparse.ArgumentDefaultsHelpFormatter):
+  pass
+
+
+def create_argument_parser(program_usage, description=''):
+  """Creates an ArgumentParser with the proper formatting.
+
+  Args:
+    program_usage: Program usage string, such as 'foo'.
+    description: Help string, usually from __doc__.
+
+  Returns:
+    An ArgumentParser that can be used to parse arguments.
+  """
+  parser = argparse.ArgumentParser(prog='manage.py serve',
+                                   description=description,
+                                   formatter_class=_ComboHelpFormatter)
+  _add_common_args(parser)
+  return parser
+
+
+def _add_common_args(parser):
+  """Adds common system arguments to an argument parser.
+
+  Args:
+    parser: ArgumentParser to modify.
+  """
+  # TODO(benvanik): logging control/etc
+  pass
+
+
+def add_common_build_args(parser, targets=False):
+  """Adds common build arguments to an argument parser.
+
+  Args:
+    parser: ArgumentParser to modify.
+    targets: True to add variable target arguments.
+  """
+  # Threading/execution control
+  parser.add_argument('-j', '--jobs',
+                      dest='jobs',
+                      type=int,
+                      default=None,
+                      help=('Specifies the number of tasks to run '
+                            'simultaneously. If omitted then all processors '
+                            'will be used.'))
+
+  # Build context control
+  parser.add_argument('-f', '--force',
+                      dest='force',
+                      action='store_true',
+                      default=False,
+                      help=('Force all rules to run as if there was no cache.'))
+  parser.add_argument('--stop_on_error',
+                      dest='stop_on_error',
+                      action='store_true',
+                      default=False,
+                      help=('Stop building when an error is encountered.'))
+
+  # Target specification
+  if targets:
+    parser.add_argument('targets',
+                        nargs='+',
+                        metavar='target',
+                        help='Target build rule (such as :a or foo/bar:a)')
+
+
+def clean_output(cwd):
+  """Cleans all build-related output and caches.
+
+  Args:
+    cwd: Current working directory.
+
+  Returns:
+    True if the clean succeeded.
+  """
+  nuke_paths = [
+      '.build-cache',
+      'build-out',
+      'build-gen',
+      'build-bin',
+      ]
+  any_failed = False
+  for path in nuke_paths:
+    full_path = os.path.join(cwd, path)
+    if os.path.isdir(full_path):
+      try:
+        shutil.rmtree(full_path)
+      except Exception as e:
+        print 'Unable to remove %s: %s' % (full_path, e)
+        any_failed = True
+  return not any_failed
+
+
+def run_build(cwd, parsed_args):
+  """Runs a build with the given arguments.
+  Assumes that add_common_args and add_common_build_args was called on the
+  ArgumentParser.
+
+  Args:
+    cwd: Current working directory.
+    parsed_args: Argument namespace from an ArgumentParser.
+  """
+  build_env = BuildEnvironment(root_path=cwd)
+
+  module_resolver = FileModuleResolver(cwd)
+  project = Project(module_resolver=module_resolver)
+
+  # -j/--jobs switch to change execution mode
+  # TODO(benvanik): force -j 1 on Cygwin?
+  if parsed_args.jobs == 1:
+    task_executor = InProcessTaskExecutor()
+  else:
+    task_executor = MultiProcessTaskExecutor(worker_count=parsed_args.jobs)
+
+  # TODO(benvanik): good logging/info - resolve rules in project and print
+  #     info?
+  print 'building %s' % (parsed_args.targets)
+
+  # TODO(benvanik): take additional args from command line
+  all_target_outputs = set([])
+  with BuildContext(build_env, project,
+                    task_executor=task_executor,
+                    force=parsed_args.force,
+                    stop_on_error=parsed_args.stop_on_error,
+                    raise_on_error=False) as build_ctx:
+    result = build_ctx.execute_sync(parsed_args.targets)
+    if result:
+      for target in parsed_args.targets:
+        (state, target_outputs) = build_ctx.get_rule_results(target)
+        all_target_outputs.update(target_outputs)
+
+  return (result == True, all_target_outputs)
diff --git a/anvil/context.py b/anvil/context.py
new file mode 100644
index 0000000..175c219
--- /dev/null
+++ b/anvil/context.py
@@ -0,0 +1,673 @@
+# Copyright 2012 Google Inc. All Rights Reserved.
+
+"""Build context.
+
+A build context is created to manage the dependency graph and build rules, as
+well as handling distribution and execution of the tasks those rules create.
+"""
+
+__author__ = 'benvanik@google.com (Ben Vanik)'
+
+
+from collections import deque
+import fnmatch
+import multiprocessing
+import os
+import stat
+
+import async
+from async import Deferred
+import graph
+import project
+import task
+import util
+
+
+class Status:
+  """Enumeration describing the status of a context."""
+  WAITING = 0
+  RUNNING = 1
+  SUCCEEDED = 2
+  FAILED = 3
+
+
+class BuildEnvironment(object):
+  """Build environment settings, containing access to all globals.
+  Build environments are a combination of flags passed to the build system
+  (from configuration files or the command line), system environment variables,
+  and platform options.
+
+  Rule and task implementations should avoid accessing the kind of information
+  contained here from anywhere else (such as the sys module), as this ensures
+  a consistent environment.
+
+  The build environment should be kept constant throughout a build, and should
+  be treated as read-only while in use by a context.
+
+  This object may be passed to other processes, and must be pickeable.
+  """
+
+  def __init__(self, root_path=None):
+    """Initializes a build environment.
+
+    Args:
+      root_path: Root path for base path resolution. If none is provided then
+          the current working directory will be used.
+
+    Raises:
+      OSError: A path was not found or is wrong type.
+    """
+    # TODO(benvanik): cwd for path resolution
+    # TODO(benvanik): environment variables
+    # TODO(benvanik): user-defined options dict
+
+    if not root_path or not len(root_path):
+      self.root_path = os.getcwd()
+    else:
+      self.root_path = os.path.abspath(root_path)
+    if not os.path.isdir(self.root_path):
+      raise OSError('Root path "%s" not found or not a directory' % (
+          self.root_path))
+
+
+class BuildContext(object):
+  """A build context for a given project and set of target rules.
+  Projects are built by specifying rules that should be considered the
+  'targets'. All rules that they depend on are then built, in the proper order,
+  to ensure that all dependencies are up to date.
+
+  Build contexts store the runtime definitions of rules, as well as the
+  environment they run in.
+
+  Build contexts are designed to be used once and thrown away. To start another
+  build create a new context with the same parameters.
+  """
+
+  def __init__(self, build_env, project,
+               task_executor=None, force=False,
+               stop_on_error=False, raise_on_error=False):
+    """Initializes a build context.
+
+    Args:
+      build_env: Current build environment.
+      project: Project to use for building.
+      task_executor: Task executor to use. One will be created if none is
+          passed.
+      force: True to force execution of tasks even if they have not changed.
+      stop_on_error: True to stop executing tasks as soon as an error occurs.
+      raise_on_error: True to rethrow exceptions to ease debugging.
+    """
+    self.build_env = build_env
+    self.project = project
+
+    self.task_executor = task_executor
+    self._close_task_executor = False
+    if not self.task_executor:
+      # HACK: multiprocessing on cygwin is really slow, so unless the caller
+      # specifies we try to use the in-process executor to keep test times
+      # low (any non-test callers should be specifying their own anyway)
+      self.task_executor = task.InProcessTaskExecutor()
+      #self.task_executor = task.MultiProcessTaskExecutor()
+      self._close_task_executor = True
+
+    self.force = force
+    self.stop_on_error = stop_on_error
+    self.raise_on_error = raise_on_error
+
+    # Build the rule graph
+    self.rule_graph = graph.RuleGraph(self.project)
+
+    # Dictionary that should be used to map rule paths to RuleContexts
+    self.rule_contexts = {}
+
+  def __enter__(self):
+    return self
+
+  def __exit__(self, type, value, traceback):
+    if self._close_task_executor:
+      self.task_executor.close()
+
+  def execute_sync(self, target_rule_names):
+    """Synchronously executes the given target rules in the context.
+    Rules are executed in the order and, where possible, in parallel.
+
+    This is equivalent to calling execute_async and then waiting on the
+    deferred.
+
+    Args:
+      target_rule_names: A list of rule names that are to be executed.
+
+    Returns:
+      A boolean indicating whether execution succeeded.
+
+    Raises:
+      KeyError: One of the given target rules was not found in the project.
+      NameError: An invalid target rule was given.
+      TypeError: An invalid target rule was given.
+      RuntimeError: Execution failed to complete.
+    """
+    d = self.execute_async(target_rule_names)
+    self.wait(d)
+    result = [None]
+    def _callback():
+      result[0] = True
+    def _errback():
+      result[0] = False
+    d.add_callback_fn(_callback)
+    d.add_errback_fn(_errback)
+    assert result[0] is not None
+    return result[0]
+
+  def execute_async(self, target_rule_names):
+    """Executes the given target rules in the context.
+    Rules are executed in the order and, where possible, in parallel.
+
+    Args:
+      target_rule_names: A list of rule names that are to be executed.
+
+    Returns:
+      A Deferred that completes when all rules have completed. If an error
+      occurs in any rule an errback will be called.
+
+    Raises:
+      KeyError: One of the given target rules was not found in the project.
+      NameError: An invalid target rule was given.
+      TypeError: An invalid target rule was given.
+    """
+    # Verify that target rules are valid and exist
+    target_rule_names = list(target_rule_names)
+    util.validate_names(target_rule_names, require_semicolon=True)
+    for rule_name in target_rule_names:
+      if not self.project.resolve_rule(rule_name):
+        raise KeyError('Target rule "%s" not found in project' % (rule_name))
+
+    # Calculate the sequence of rules to execute
+    rule_sequence = self.rule_graph.calculate_rule_sequence(target_rule_names)
+
+    any_failed = [False]
+    main_deferred = Deferred()
+    remaining_rules = deque(rule_sequence)
+    in_flight_rules = []
+
+    def _issue_rule(rule):
+      """Issues a single rule into the current execution context.
+      Updates the in_flight_rules list and pumps when the rule completes.
+
+      Args:
+        rule: Rule to issue.
+      """
+      def _rule_callback(*args, **kwargs):
+        in_flight_rules.remove(rule)
+        _pump(previous_succeeded=True)
+
+      def _rule_errback(exception=None, *args, **kwargs):
+        in_flight_rules.remove(rule)
+        # TODO(benvanik): log result/exception/etc?
+        if exception: # pragma: no cover
+          print exception
+        _pump(previous_succeeded=False)
+
+      in_flight_rules.append(rule)
+      rule_deferred = self._execute_rule(rule)
+      rule_deferred.add_callback_fn(_rule_callback)
+      rule_deferred.add_errback_fn(_rule_errback)
+      return rule_deferred
+
+    def _pump(previous_succeeded=True):
+      """Attempts to run another rule and signals the main_deferred if done.
+
+      Args:
+        previous_succeeded: Whether the previous rule succeeded.
+      """
+      # If we're already done, gracefully exit
+      if main_deferred.is_done():
+        return
+
+      # If we failed and we are supposed to stop, gracefully stop by
+      # killing all future rules
+      # This is better than terminating immediately, as it allows legit tasks
+      # to finish
+      if not previous_succeeded:
+        any_failed[0] = True
+      if not previous_succeeded and self.stop_on_error:
+        remaining_rules.clear()
+
+      if len(remaining_rules):
+        # Peek the next rule
+        next_rule = remaining_rules[0]
+
+        # See if it has any dependency on currently running rules
+        for in_flight_rule in in_flight_rules:
+          if self.rule_graph.has_dependency(next_rule.path,
+                                            in_flight_rule.path):
+            # Blocked on a previous rule, so pass and wait for the next pump
+            return
+
+        # If here then we found no conflicting rules, so run!
+        remaining_rules.popleft()
+        _issue_rule(next_rule)
+      else:
+        # Done!
+        # TODO(benvanik): better errbacks? some kind of BuildResults?
+        if not any_failed[0]:
+          main_deferred.callback()
+        else:
+          main_deferred.errback()
+
+    # Kick off execution (once for each rule as a heuristic for flooding the
+    # pipeline)
+    for rule in rule_sequence:
+      _pump()
+
+    return main_deferred
+
+  def wait(self, deferreds):
+    """Blocks waiting on a list of deferreds until they all complete.
+    The deferreds must have been returned from execute.
+
+    Args:
+      deferreds: A list of Deferreds (or one).
+    """
+    self.task_executor.wait(deferreds)
+
+  def _execute_rule(self, rule):
+    """Executes a single rule.
+    This assumes that all dependent rules have already been executed. Assertions
+    will be raised if all dependent rules have not completed successfully or
+    if the given rule has been executed already.
+
+    Args:
+      rule: Rule to execute.
+
+    Returns:
+      A Deferred that will callback when the rule has completed executing.
+    """
+    assert not self.rule_contexts.has_key(rule.path)
+    rule_ctx = rule.create_context(self)
+    self.rule_contexts[rule.path] = rule_ctx
+    if rule_ctx.check_predecessor_failures():
+      return rule_ctx.cascade_failure()
+    else:
+      rule_ctx.begin()
+      return rule_ctx.deferred
+
+  def get_rule_results(self, rule):
+    """Gets the status/output of a rule.
+    This is not thread safe and should only be used to query the result of a
+    rule after it has been run.
+
+    Args:
+      rule: Rule to query - can be a Rule object or a rule path that will be
+          resolved.
+
+    Returns:
+      A tuple containing (status, output_paths) for the given rule.
+
+    Raises:
+      KeyError: The rule was not found.
+    """
+    if isinstance(rule, str):
+      rule = self.project.resolve_rule(rule)
+    if self.rule_contexts.has_key(rule.path):
+      rule_ctx = self.rule_contexts[rule.path]
+      return (rule_ctx.status, rule_ctx.all_output_files[:])
+    else:
+      return (Status.WAITING, [])
+
+  def get_rule_outputs(self, rule):
+    """Gets the output files of the given rule.
+    It is only valid to call this on rules that have already been executed
+    and have succeeded.
+
+    Args:
+      rule: Rule to query - can be a Rule object or a rule path that will be
+          resolved.
+
+    Returns:
+      A list of all output files from the rule or None if the rule did not yet
+      execute.
+    Raises:
+      KeyError: The rule was not found.
+    """
+    results = self.get_rule_results(rule)
+    return results[1]
+
+
+class RuleContext(object):
+  """A runtime context for an individual rule.
+  Must contain all of the state for a rule while it is being run, including
+  all resolved inputs and resulting outputs (once complete).
+  """
+
+  def __init__(self, build_context, rule, *args, **kwargs):
+    """Initializes a rule context.
+
+    Args:
+      build_context: BuildContext this rule is running in.
+      rule: Rule this context wraps.
+    """
+    self.build_context = build_context
+    self.build_env = build_context.build_env
+    self.rule = rule
+
+    self.deferred = Deferred()
+    self.status = Status.WAITING
+    self.start_time = None
+    self.end_time = None
+    self.exception = None
+
+    # TODO(benvanik): logger
+    self.logger = None
+
+    # Resolve all src paths
+    # If rules have their own attrs they'll have to do them themselves
+    self.src_paths = self._resolve_input_files(rule.srcs, apply_src_filter=True)
+
+    # This list of all files this rule outputted, upon completion
+    self.all_output_files = []
+
+  def _resolve_input_files(self, paths, apply_src_filter=False):
+    """Resolves the given paths into real file system paths, ready for use.
+    This adds direct file references, recursively enumerates paths, expands
+    globs, and grabs outputs from other rules.
+
+    Since this actually checks to see if specific files are present and raises
+    if not, this should be called in the initializer of all subclasses to
+    resolve all paths in a place where a good stack will occur.
+
+    Note that the resulting list is not deduplicated - certain rules may want
+    the exact list in the exact order defined. If you want a de-duped list,
+    simply use list(set(result)) to quickly de-dupe.
+
+    Args:
+      paths: Paths to resolve.
+
+    Returns:
+      A list of all file paths from the given paths.
+
+    Raises:
+      KeyError: A required rule was not found.
+      OSError: A source path was not found or could not be accessed.
+      RuntimeError: Internal runtime error (rule executed out of order/etc)
+    """
+    base_path = os.path.dirname(self.rule.parent_module.path)
+    input_paths = []
+    for src in paths:
+      # Grab all items from the source
+      src_items = None
+      if util.is_rule_path(src):
+        # Reference to another rule
+        other_rule = self.build_context.project.resolve_rule(
+            src, requesting_module=self.rule.parent_module)
+        if not other_rule:
+          raise KeyError('Source rule "%s" not found' % (src))
+        if not self.build_context.rule_contexts.has_key(other_rule.path):
+          raise RuntimeError('Source rule "%s" not yet executed' % (src))
+        other_rule_ctx = self.build_context.rule_contexts[other_rule.path]
+        src_items = other_rule_ctx.all_output_files
+      else:
+        # File or folder path
+        src_path = os.path.join(base_path, src)
+        mode = os.stat(src_path).st_mode
+        if stat.S_ISDIR(mode):
+          src_items = os.listdir(src_path)
+        else:
+          src_items = [src_path]
+
+      # Apply the src_filter, if any
+      if apply_src_filter and self.rule.src_filter:
+        for file_path in src_items:
+          if fnmatch.fnmatch(file_path, self.rule.src_filter):
+            input_paths.append(file_path)
+      else:
+        input_paths.extend(src_items)
+    return input_paths
+
+  def __get_target_path(self, base_path, name=None, suffix=None):
+    """Handling of _get_*_path() methods.
+
+    Args:
+      base_path: Base path to the project root.
+      name: If a name is provided it will be used instead of the rule name.
+      suffix: Suffix to add to whatever path is built, such as '.txt' to add
+          an extension.
+
+    Returns:
+      A full path that can be used to write a file.
+    """
+    if not name or not len(name):
+      name = self.rule.name
+    if suffix and len(suffix):
+      name += suffix
+    root_path = self.build_context.build_env.root_path
+    module_path = os.path.dirname(self.rule.parent_module.path)
+    rel_path = os.path.relpath(module_path, root_path)
+    return os.path.normpath(os.path.join(base_path, rel_path, name))
+
+  def _get_out_path(self, name=None, suffix=None):
+    """Gets the 'out' path for an output.
+    If no name is provided then the rule name will be used.
+
+    The 'out' path should be used for all content/binary results.
+
+    Args:
+      name: If a name is provided it will be used instead of the rule name.
+      suffix: Suffix to add to whatever path is built, such as '.txt' to add
+          an extension.
+
+    Returns:
+      A full path that can be used to write a file to the proper 'out' path.
+    """
+    base_path = os.path.join(self.build_context.build_env.root_path,
+                             'build-out')
+    return self.__get_target_path(base_path, name=name, suffix=suffix)
+
+  def _get_gen_path(self, name=None, suffix=None):
+    """Gets the 'gen' path for an output.
+    If no name is provided then the rule name will be used.
+
+    The 'gen' path should be used for generated code only.
+
+    Args:
+      name: If a name is provided it will be used instead of the rule name.
+      suffix: Suffix to add to whatever path is built, such as '.txt' to add
+          an extension.
+
+    Returns:
+      A full path that can be used to write a file to the proper 'gen' path.
+    """
+    base_path = os.path.join(self.build_context.build_env.root_path,
+                             'build-gen')
+    return self.__get_target_path(base_path, name=name, suffix=suffix)
+
+  def __get_target_path_for_src(self, base_path, src, opt_path=None):
+    """Handling of _get_*_path_for_src() methods.
+
+    Args:
+      base_path: Base path to the project root.
+      src: Absolute source path.
+
+    Returns:
+      A full path that can be used to write a file.
+    """
+    root_path = self.build_context.build_env.root_path
+    rel_path = os.path.relpath(src, root_path)
+    # Need to strip build-out and build-gen (so we can reference any file)
+    rel_path = rel_path.replace('build-out/', '').replace('build-gen/', '')
+    return os.path.normpath(os.path.join(base_path, rel_path))
+
+  def _get_out_path_for_src(self, src):
+    """Gets the 'out' path for a source file.
+
+    The 'out' path should be used for all content/binary results.
+
+    Args:
+      src: Absolute source path.
+
+    Returns:
+      A full path that can be used to write a file to the proper 'out' path.
+    """
+    base_path = os.path.join(self.build_context.build_env.root_path,
+                             'build-out')
+    return self.__get_target_path_for_src(base_path, src)
+
+  def _get_gen_path_for_src(self, src):
+    """Gets the 'gen' path for a source file.
+
+    The 'gen' path should be used for generated code only.
+
+    Args:
+      src: Absolute source path.
+
+    Returns:
+      A full path that can be used to write a file to the proper 'gen' path.
+    """
+    base_path = os.path.join(self.build_context.build_env.root_path,
+                             'build-gen')
+    return self.__get_target_path_for_src(base_path, src)
+
+  def _ensure_output_exists(self, path):
+    """Makes the given path exist, if it doesn't.
+
+    Arg:
+      path: An absolute path to a folder that should exist.
+    """
+    if not os.path.isdir(path):
+      os.makedirs(path)
+
+  def _append_output_paths(self, paths):
+    """Appends the given paths to the output list.
+    Other rules that depend on this rule will receive these paths when it
+    is used as a source.
+
+    Args:
+      paths: A list of paths to add to the list.
+    """
+    self.all_output_files.extend(paths)
+
+  def _run_task_async(self, task):
+    """Runs a task asynchronously.
+    This is a utility method that makes it easier to execute tasks.
+
+    Args:
+      task: Task to execute.
+
+    Returns:
+      A deferred that signals when the task completes.
+    """
+    return self.build_context.task_executor.run_task_async(task)
+
+  def check_predecessor_failures(self):
+    """Checks all dependencies for failure.
+
+    Returns:
+      True if any dependency has failed.
+    """
+    for dep in self.rule.get_dependent_paths():
+      if util.is_rule_path(dep):
+        other_rule = self.build_context.project.resolve_rule(
+            dep, requesting_module=self.rule.parent_module)
+        other_rule_ctx = self.build_context.rule_contexts.get(
+            other_rule.path, None)
+        if other_rule_ctx.status == Status.FAILED:
+          return True
+    return False
+
+  def begin(self):
+    """Begins asynchronous rule execution.
+    Custom RuleContext implementations should override this method to perform
+    their behavior (spawning tasks/etc). When the returned Deferred is called
+    back the rule context should be completed, with all_output_files properly
+    set.
+
+    The default implementation ends immediately, passing all input files through
+    as output.
+
+    Returns:
+      A Deferred that can will be called back when the rule has completed.
+    """
+    self.status = Status.RUNNING
+    self.start_time = util.timer()
+    return self.deferred
+
+  def cascade_failure(self):
+    """Instantly fails a rule, signaling that a rule prior to it has failed
+    and it should not be run.
+
+    Use this if a call to check_predecessor_failures returns True to properly
+    set a rule context up for cascading failures.
+    After calling this begin should not be called.
+
+    Returns:
+      A Deferred that has had its errback called.
+    """
+    # TODO(benvanik): special CascadingError exception
+    self.start_time = util.timer()
+    self._fail()
+    return self.deferred
+
+  def _succeed(self):
+    """Signals that rule execution has completed successfully.
+    This will set all state and issue the callback on the deferred.
+    """
+    self.status = Status.SUCCEEDED
+    self.end_time = util.timer()
+    self.deferred.callback()
+
+  def _fail(self, exception=None, *args, **kwargs):
+    """Signals that rule execution has completed in failure.
+    This will set all state and issue the errback on the deferred.
+    If an exception is provided it will be set on the context and passed as
+    the first argument to the deferred.
+
+    Args:
+      exception: The exception that resulted in the rule failure, if any.
+    """
+    self.status = Status.FAILED
+    self.end_time = util.timer()
+    self.exception = exception
+    if exception:
+      self.deferred.errback(exception=exception)
+    else:
+      self.deferred.errback()
+
+  def _chain(self, deferreds):
+    """Chains the completion of the rule on the given deferred.
+    Depending on the success or failure the deferred, the rule context will
+    succeeed or fail.
+
+    Args:
+      deferred: A Deferred or list of deferreds that will be called back.
+    """
+    deferred = async.gather_deferreds(deferreds, errback_if_any_fail=True)
+    def _callback(*args, **kwargs):
+      self._succeed()
+    def _errback(*args, **kwargs):
+      exception = None
+      for arg in args[0]:
+        if not arg[0]:
+          if len(arg[1]) and isinstance(arg[1][0], Exception):
+            exception = arg[1][0]
+            break
+          exception = arg[2].get('exception', None)
+          if exception:
+            break
+      self._fail(exception=exception)
+    deferred.add_callback_fn(_callback)
+    deferred.add_errback_fn(_errback)
+
+
+# class FileDelta(object):
+#   """
+#   TODO(benvanik): move to another module and setup to use cache
+#   """
+
+#   def __init__(self, source_paths=None):
+#     """
+#     Args:
+#       source_paths
+#     """
+#     self.all_files = []
+#     self.added_files = []
+#     self.removed_files = []
+#     self.changed_files = []
diff --git a/anvil/context_test.py b/anvil/context_test.py
new file mode 100755
index 0000000..d2d3017
--- /dev/null
+++ b/anvil/context_test.py
@@ -0,0 +1,448 @@
+#!/usr/bin/python
+
+# Copyright 2012 Google Inc. All Rights Reserved.
+
+"""Tests for the context module.
+"""
+
+__author__ = 'benvanik@google.com (Ben Vanik)'
+
+
+import os
+import unittest2
+
+import async
+from context import *
+from module import *
+from rule import *
+from project import *
+from task import *
+from test import AsyncTestCase, FixtureTestCase
+
+
+class BuildEnvironmentTest(FixtureTestCase):
+  """Behavioral tests of the BuildEnvironment type."""
+  fixture='simple'
+
+  def testConstruction(self):
+    build_env = BuildEnvironment()
+    self.assertTrue(os.path.isdir(build_env.root_path))
+
+    build_env = BuildEnvironment(root_path='.')
+    self.assertTrue(os.path.isdir(build_env.root_path))
+
+    build_env = BuildEnvironment(root_path=self.root_path)
+    self.assertTrue(os.path.isdir(build_env.root_path))
+    self.assertEqual(build_env.root_path, self.root_path)
+
+    build_env = BuildEnvironment(root_path=os.path.join(self.root_path, 'dir'))
+    self.assertTrue(os.path.isdir(build_env.root_path))
+    self.assertEqual(build_env.root_path, os.path.join(self.root_path, 'dir'))
+
+    with self.assertRaises(OSError):
+      BuildEnvironment(root_path='/not/found')
+
+class BuildContextTest(FixtureTestCase):
+  """Behavioral tests of the BuildContext type."""
+  fixture = 'simple'
+
+  def setUp(self):
+    super(BuildContextTest, self).setUp()
+    self.build_env = BuildEnvironment(root_path=self.root_path)
+
+  def testConstruction(self):
+    project = Project()
+    with BuildContext(self.build_env, project): pass
+
+    project = Project(modules=[Module('m', rules=[Rule('a')])])
+    with BuildContext(self.build_env, project) as ctx:
+      self.assertIsNotNone(ctx.task_executor)
+
+    with BuildContext(self.build_env, project,
+                      task_executor=InProcessTaskExecutor()) as ctx:
+      self.assertIsNotNone(ctx.task_executor)
+
+  def testExecution(self):
+    project = Project(module_resolver=FileModuleResolver(self.root_path))
+
+    with BuildContext(self.build_env, project) as ctx:
+      with self.assertRaises(NameError):
+        ctx.execute_async(['x'])
+      with self.assertRaises(KeyError):
+        ctx.execute_async([':x'])
+      with self.assertRaises(OSError):
+        ctx.execute_async(['x:x'])
+
+    with BuildContext(self.build_env, project) as ctx:
+      self.assertTrue(ctx.execute_sync([':a']))
+      results = ctx.get_rule_results(':a')
+      self.assertEqual(results[0], Status.SUCCEEDED)
+
+    with BuildContext(self.build_env, project) as ctx:
+      d = ctx.execute_async([':a'])
+      ctx.wait(d)
+      self.assertCallback(d)
+      results = ctx.get_rule_results(':a')
+      self.assertEqual(results[0], Status.SUCCEEDED)
+
+    with BuildContext(self.build_env, project) as ctx:
+      d = ctx.execute_async([':mixed_input'])
+      ctx.wait(d)
+      self.assertCallback(d)
+      results = ctx.get_rule_results(':mixed_input')
+      self.assertEqual(results[0], Status.SUCCEEDED)
+      self.assertEqual(len(results[1]), 2)
+
+    class SucceedRule(Rule):
+      class _Context(RuleContext):
+        def begin(self):
+          super(SucceedRule._Context, self).begin()
+          #print 'hello from rule %s' % (self.rule.path)
+          self._succeed()
+    class FailRule(Rule):
+      class _Context(RuleContext):
+        def begin(self):
+          super(FailRule._Context, self).begin()
+          #print 'hello from rule %s' % (self.rule.path)
+          self._fail()
+
+    project = Project(modules=[Module('m', rules=[SucceedRule('a')])])
+    with BuildContext(self.build_env, project) as ctx:
+      d = ctx.execute_async(['m:a'])
+      ctx.wait(d)
+      self.assertCallback(d)
+      results = ctx.get_rule_results('m:a')
+      self.assertEqual(results[0], Status.SUCCEEDED)
+
+    project = Project(modules=[Module('m', rules=[
+        SucceedRule('a'),
+        SucceedRule('b', deps=[':a'])])])
+    with BuildContext(self.build_env, project) as ctx:
+      d = ctx.execute_async(['m:b'])
+      ctx.wait(d)
+      self.assertCallback(d)
+      results = ctx.get_rule_results('m:a')
+      self.assertEqual(results[0], Status.SUCCEEDED)
+      results = ctx.get_rule_results('m:b')
+      self.assertEqual(results[0], Status.SUCCEEDED)
+
+    project = Project(modules=[Module('m', rules=[FailRule('a')])])
+    with BuildContext(self.build_env, project) as ctx:
+      d = ctx.execute_async(['m:a'])
+      ctx.wait(d)
+      self.assertErrback(d)
+      results = ctx.get_rule_results('m:a')
+      self.assertEqual(results[0], Status.FAILED)
+
+    project = Project(modules=[Module('m', rules=[FailRule('a')])])
+    with BuildContext(self.build_env, project) as ctx:
+      self.assertFalse(ctx.execute_sync(['m:a']))
+      results = ctx.get_rule_results('m:a')
+      self.assertEqual(results[0], Status.FAILED)
+
+    project = Project(modules=[Module('m', rules=[
+        FailRule('a'),
+        SucceedRule('b', deps=[':a'])])])
+    with BuildContext(self.build_env, project) as ctx:
+      d = ctx.execute_async(['m:b'])
+      ctx.wait(d)
+      self.assertErrback(d)
+      results = ctx.get_rule_results('m:a')
+      self.assertEqual(results[0], Status.FAILED)
+      results = ctx.get_rule_results('m:b')
+      self.assertEqual(results[0], Status.FAILED)
+
+    project = Project(modules=[Module('m', rules=[
+        FailRule('a'),
+        SucceedRule('b', deps=[':a'])])])
+    with BuildContext(self.build_env, project, stop_on_error=True) as ctx:
+      d = ctx.execute_async(['m:b'])
+      ctx.wait(d)
+      self.assertErrback(d)
+      results = ctx.get_rule_results('m:a')
+      self.assertEqual(results[0], Status.FAILED)
+      results = ctx.get_rule_results('m:b')
+      self.assertEqual(results[0], Status.WAITING)
+
+    # TODO(benvanik): test stop_on_error
+    # TODO(benvanik): test raise_on_error
+
+  def testCaching(self):
+    # TODO(benvanik): test caching and force arg
+    pass
+
+  def testBuild(self):
+    project = Project(module_resolver=FileModuleResolver(self.root_path))
+
+    with BuildContext(self.build_env, project) as ctx:
+      d = ctx.execute_async([':a'])
+      ctx.wait(d)
+      self.assertCallback(d)
+      # TODO(benvanik): the rest of this
+
+
+class RuleContextTest(FixtureTestCase):
+  """Behavioral tests of the RuleContext type."""
+  fixture = 'simple'
+
+  def setUp(self):
+    super(RuleContextTest, self).setUp()
+    self.build_env = BuildEnvironment(root_path=self.root_path)
+
+  def testStatus(self):
+    project = Project(module_resolver=FileModuleResolver(self.root_path))
+    build_ctx = BuildContext(self.build_env, project)
+    project = Project(module_resolver=FileModuleResolver(self.root_path))
+    rule = project.resolve_rule(':a')
+
+    class SuccessfulRuleContext(RuleContext):
+      def begin(self):
+        super(SuccessfulRuleContext, self).begin()
+        self._succeed()
+
+    rule_ctx = SuccessfulRuleContext(build_ctx, rule)
+    self.assertEqual(rule_ctx.status, Status.WAITING)
+    rule_ctx.begin()
+    self.assertTrue(rule_ctx.deferred.is_done())
+    self.assertEqual(rule_ctx.status, Status.SUCCEEDED)
+
+    class FailedRuleContext(RuleContext):
+      def begin(self):
+        super(FailedRuleContext, self).begin()
+        self._fail()
+
+    rule_ctx = FailedRuleContext(build_ctx, rule)
+    self.assertEqual(rule_ctx.status, Status.WAITING)
+    rule_ctx.begin()
+    self.assertTrue(rule_ctx.deferred.is_done())
+    self.assertEqual(rule_ctx.status, Status.FAILED)
+    self.assertIsNone(rule_ctx.exception)
+
+    class FailedWithErrorRuleContext(RuleContext):
+      def begin(self):
+        super(FailedWithErrorRuleContext, self).begin()
+        self._fail(RuntimeError('Failure'))
+
+    rule_ctx = FailedWithErrorRuleContext(build_ctx, rule)
+    self.assertEqual(rule_ctx.status, Status.WAITING)
+    rule_ctx.begin()
+    self.assertTrue(rule_ctx.deferred.is_done())
+    self.assertEqual(rule_ctx.status, Status.FAILED)
+    self.assertIsInstance(rule_ctx.exception, RuntimeError)
+
+    class SuccessfulAsyncRuleContext(RuleContext):
+      def begin(self):
+        super(SuccessfulAsyncRuleContext, self).begin()
+        d = Deferred()
+        self._chain(d)
+        d.callback()
+
+    rule_ctx = SuccessfulAsyncRuleContext(build_ctx, rule)
+    self.assertEqual(rule_ctx.status, Status.WAITING)
+    rule_ctx.begin()
+    self.assertTrue(rule_ctx.deferred.is_done())
+    self.assertEqual(rule_ctx.status, Status.SUCCEEDED)
+
+    class FailedAsyncRuleContext(RuleContext):
+      def begin(self):
+        super(FailedAsyncRuleContext, self).begin()
+        d = Deferred()
+        self._chain(d)
+        d.errback(RuntimeError('Failure'))
+
+    rule_ctx = FailedAsyncRuleContext(build_ctx, rule)
+    self.assertEqual(rule_ctx.status, Status.WAITING)
+    rule_ctx.begin()
+    self.assertTrue(rule_ctx.deferred.is_done())
+    self.assertEqual(rule_ctx.status, Status.FAILED)
+    self.assertIsInstance(rule_ctx.exception, RuntimeError)
+
+    class FailedManyAsyncRuleContext(RuleContext):
+      def begin(self):
+        super(FailedManyAsyncRuleContext, self).begin()
+        d1 = Deferred()
+        d2 = Deferred()
+        self._chain([d1, d2])
+        d1.callback()
+        d2.errback(RuntimeError('Failure'))
+
+    rule_ctx = FailedManyAsyncRuleContext(build_ctx, rule)
+    self.assertEqual(rule_ctx.status, Status.WAITING)
+    rule_ctx.begin()
+    self.assertTrue(rule_ctx.deferred.is_done())
+    self.assertEqual(rule_ctx.status, Status.FAILED)
+    self.assertIsInstance(rule_ctx.exception, RuntimeError)
+
+  def testFileInputs(self):
+    project = Project(module_resolver=FileModuleResolver(self.root_path))
+    build_ctx = BuildContext(self.build_env, project)
+
+    rule = project.resolve_rule(':file_input')
+    d = build_ctx._execute_rule(rule)
+    self.assertTrue(d.is_done())
+    rule_outputs = build_ctx.get_rule_outputs(rule)
+    self.assertEqual(
+        set([os.path.basename(f) for f in rule_outputs]),
+        set(['a.txt']))
+
+    rule = project.resolve_rule(':local_txt')
+    d = build_ctx._execute_rule(rule)
+    self.assertTrue(d.is_done())
+    rule_outputs = build_ctx.get_rule_outputs(rule)
+    self.assertEqual(
+        set([os.path.basename(f) for f in rule_outputs]),
+        set(['a.txt', 'b.txt', 'c.txt']))
+
+    rule = project.resolve_rule(':recursive_txt')
+    d = build_ctx._execute_rule(rule)
+    self.assertTrue(d.is_done())
+    rule_outputs = build_ctx.get_rule_outputs(rule)
+    self.assertEqual(
+        set([os.path.basename(f) for f in rule_outputs]),
+        set(['a.txt', 'b.txt', 'c.txt', 'd.txt', 'e.txt']))
+
+  def testFileInputFilters(self):
+    project = Project(module_resolver=FileModuleResolver(self.root_path))
+    build_ctx = BuildContext(self.build_env, project)
+
+    rule = project.resolve_rule(':missing_txt')
+    with self.assertRaises(OSError):
+      build_ctx._execute_rule(rule)
+
+    rule = project.resolve_rule(':missing_glob_txt')
+    d = build_ctx._execute_rule(rule)
+    self.assertTrue(d.is_done())
+    rule_outputs = build_ctx.get_rule_outputs(rule)
+    self.assertEqual(len(rule_outputs), 0)
+
+    rule = project.resolve_rule(':local_txt_filter')
+    d = build_ctx._execute_rule(rule)
+    self.assertTrue(d.is_done())
+    rule_outputs = build_ctx.get_rule_outputs(rule)
+    self.assertEqual(
+        set([os.path.basename(f) for f in rule_outputs]),
+        set(['a.txt', 'b.txt', 'c.txt']))
+
+    rule = project.resolve_rule(':recursive_txt_filter')
+    d = build_ctx._execute_rule(rule)
+    self.assertTrue(d.is_done())
+    rule_outputs = build_ctx.get_rule_outputs(rule)
+    self.assertEqual(
+        set([os.path.basename(f) for f in rule_outputs]),
+        set(['a.txt', 'b.txt', 'c.txt', 'd.txt', 'e.txt']))
+
+  def testRuleInputs(self):
+    project = Project(module_resolver=FileModuleResolver(self.root_path))
+    build_ctx = BuildContext(self.build_env, project)
+
+    rule = project.resolve_rule(':file_input')
+    d = build_ctx._execute_rule(rule)
+    self.assertTrue(d.is_done())
+    rule_outputs = build_ctx.get_rule_outputs(rule)
+    self.assertNotEqual(len(rule_outputs), 0)
+
+    rule = project.resolve_rule(':rule_input')
+    d = build_ctx._execute_rule(rule)
+    self.assertTrue(d.is_done())
+    rule_outputs = build_ctx.get_rule_outputs(rule)
+    self.assertEqual(
+        set([os.path.basename(f) for f in rule_outputs]),
+        set(['a.txt']))
+
+    rule = project.resolve_rule(':mixed_input')
+    d = build_ctx._execute_rule(rule)
+    self.assertTrue(d.is_done())
+    rule_outputs = build_ctx.get_rule_outputs(rule)
+    self.assertEqual(
+        set([os.path.basename(f) for f in rule_outputs]),
+        set(['a.txt', 'b.txt']))
+
+    rule = project.resolve_rule(':missing_input')
+    with self.assertRaises(KeyError):
+      build_ctx._execute_rule(rule)
+
+    build_ctx = BuildContext(self.build_env, project)
+    rule = project.resolve_rule(':rule_input')
+    with self.assertRaises(RuntimeError):
+      build_ctx._execute_rule(rule)
+
+  def _compare_path(self, result, expected):
+    result = os.path.relpath(result, self.root_path)
+    self.assertEqual(result, expected)
+
+  def testTargetPaths(self):
+    project = Project(module_resolver=FileModuleResolver(self.root_path))
+    build_ctx = BuildContext(self.build_env, project)
+
+    class SuccessfulRuleContext(RuleContext):
+      def begin(self):
+        super(SuccessfulRuleContext, self).begin()
+        self._succeed()
+
+    rule = project.resolve_rule(':a')
+    rule_ctx = SuccessfulRuleContext(build_ctx, rule)
+    self._compare_path(
+        rule_ctx._get_out_path(), 'build-out/a')
+    self._compare_path(
+        rule_ctx._get_out_path(suffix='.txt'), 'build-out/a.txt')
+    self._compare_path(
+        rule_ctx._get_out_path('f'), 'build-out/f')
+    self._compare_path(
+        rule_ctx._get_out_path('f', suffix='.txt'), 'build-out/f.txt')
+    self._compare_path(
+        rule_ctx._get_out_path('dir/f'), 'build-out/dir/f')
+    # Note that both are implemented the same way
+    self._compare_path(
+        rule_ctx._get_gen_path(), 'build-gen/a')
+    self._compare_path(
+        rule_ctx._get_gen_path(suffix='.txt'), 'build-gen/a.txt')
+    self._compare_path(
+        rule_ctx._get_gen_path('f'), 'build-gen/f')
+    self._compare_path(
+        rule_ctx._get_gen_path('f', suffix='.txt'), 'build-gen/f.txt')
+    self._compare_path(
+        rule_ctx._get_gen_path('dir/f'), 'build-gen/dir/f')
+
+    rule = project.resolve_rule('dir/dir_2:d')
+    rule_ctx = SuccessfulRuleContext(build_ctx, rule)
+    self._compare_path(
+        rule_ctx._get_out_path(), 'build-out/dir/dir_2/d')
+    self._compare_path(
+        rule_ctx._get_out_path(suffix='.txt'), 'build-out/dir/dir_2/d.txt')
+    self._compare_path(
+        rule_ctx._get_out_path('f'), 'build-out/dir/dir_2/f')
+    self._compare_path(
+        rule_ctx._get_out_path('f', suffix='.txt'), 'build-out/dir/dir_2/f.txt')
+    self._compare_path(
+        rule_ctx._get_out_path('dir/f'), 'build-out/dir/dir_2/dir/f')
+
+  def testTargetSrcPaths(self):
+    project = Project(module_resolver=FileModuleResolver(self.root_path))
+    build_ctx = BuildContext(self.build_env, project)
+
+    class SuccessfulRuleContext(RuleContext):
+      def begin(self):
+        super(SuccessfulRuleContext, self).begin()
+        self._succeed()
+
+    rule = project.resolve_rule(':a')
+    rule_ctx = SuccessfulRuleContext(build_ctx, rule)
+    self._compare_path(
+        rule_ctx._get_out_path_for_src(os.path.join(self.root_path, 'a.txt')),
+        'build-out/a.txt')
+    self._compare_path(
+        rule_ctx._get_out_path_for_src(os.path.join(self.root_path,
+                                                    'dir/a.txt')),
+        'build-out/dir/a.txt')
+    # Note that both are implemented the same way
+    self._compare_path(
+        rule_ctx._get_gen_path_for_src(os.path.join(self.root_path, 'a.txt')),
+        'build-gen/a.txt')
+    self._compare_path(
+        rule_ctx._get_gen_path_for_src(os.path.join(self.root_path,
+                                                    'dir/a.txt')),
+        'build-gen/dir/a.txt')
+
+
+if __name__ == '__main__':
+  unittest2.main()
diff --git a/anvil/graph.py b/anvil/graph.py
new file mode 100644
index 0000000..989183a
--- /dev/null
+++ b/anvil/graph.py
@@ -0,0 +1,210 @@
+# Copyright 2012 Google Inc. All Rights Reserved.
+
+"""Rule dependency graph.
+
+A rule graph represents all of the rules in a project as they have been resolved
+and tracked for dependencies. The graph can then be queried for various
+information such as build rule sets/etc.
+"""
+
+__author__ = 'benvanik@google.com (Ben Vanik)'
+
+
+import networkx as nx
+
+import project
+import util
+
+
+class RuleGraph(object):
+  """A graph of rule nodes.
+  """
+
+  def __init__(self, project):
+    """Initializes a rule graph.
+
+    Args:
+      project: Project to use for resolution.
+    """
+    self.project = project
+    self.graph = nx.DiGraph()
+    # A map of rule paths to nodes, if they exist
+    self.rule_nodes = {}
+
+  def has_dependency(self, rule_path, predecessor_rule_path):
+    """Checks to see if the given rule has a dependency on another rule.
+
+    Args:
+      rule_path: The name of the rule to check.
+      predecessor_rule_path: A potential predecessor rule.
+
+    Returns:
+      True if by any way rule_path depends on predecessor_rule_path.
+
+    Raises:
+      KeyError: One of the given rules was not found.
+    """
+    rule_node = self.rule_nodes.get(rule_path, None)
+    if not rule_node:
+      raise KeyError('Rule "%s" not found' % (rule_path))
+    predecessor_rule_node = self.rule_nodes.get(predecessor_rule_path, None)
+    if not predecessor_rule_node:
+      raise KeyError('Rule "%s" not found' % (predecessor_rule_path))
+    return nx.has_path(self.graph, predecessor_rule_node, rule_node)
+
+  def _ensure_rules_present(self, rule_paths, requesting_module=None):
+    """Ensures that the given list of rules are present in the graph, and if not
+    recursively loads them.
+
+    Args:
+      rule_paths: A list of target rule paths to add to the graph.
+      requesting_module: Module that is requesting the given rules or None if
+          all rule paths are absolute.
+    """
+    # Add all of the rules listed
+    rules = []
+    for rule_path in rule_paths:
+      # Attempt to resolve the rule
+      rule = self.project.resolve_rule(rule_path,
+                                       requesting_module=requesting_module)
+      if not rule:
+        raise KeyError('Rule "%s" unable to be resolved' % (rule_path))
+      rules.append(rule)
+
+      # If already present, ignore (no need to recurse)
+      if self.rule_nodes.has_key(rule.path):
+        continue
+
+      # Wrap with our node and add it to the graph
+      rule_node = _RuleNode(rule)
+      self.rule_nodes[rule.path] = rule_node
+      self.graph.add_node(rule_node)
+
+      # Recursively resolve all dependent rules
+      dependent_rule_paths = []
+      for dep in rule.get_dependent_paths():
+        if util.is_rule_path(dep):
+          dependent_rule_paths.append(dep)
+      if len(dependent_rule_paths):
+        self._ensure_rules_present(dependent_rule_paths,
+                                   requesting_module=rule.parent_module)
+
+    # Add edges for all of the requested rules (at this point, all rules should
+    # be added to the graph)
+    for rule in rules:
+      rule_node = self.rule_nodes[rule.path]
+      for dep in rule_node.rule.get_dependent_paths():
+        if util.is_rule_path(dep):
+          dep_rule = self.project.resolve_rule(dep,
+              requesting_module=rule.parent_module)
+          dep_node = self.rule_nodes.get(dep_rule.path, None)
+          # Node should exist due to recursive addition above
+          assert dep_node
+          self.graph.add_edge(dep_node, rule_node)
+
+    # Ensure the graph is a DAG (no cycles)
+    if not nx.is_directed_acyclic_graph(self.graph):
+      # TODO(benvanik): use nx.simple_cycles() to print the cycles
+      raise ValueError('Cycle detected in the rule graph: %s' % (
+          nx.simple_cycles(self.graph)))
+
+  def add_rules_from_module(self, module):
+    """Adds all rules (and their dependencies) from the given module.
+
+    Args:
+      module: A module with rules to add.
+    """
+    rule_paths = []
+    for rule in module.rule_iter():
+      rule_paths.append(rule.path)
+    self._ensure_rules_present(rule_paths, requesting_module=module)
+
+  def has_rule(self, rule_path):
+    """Whether the graph has the given rule loaded.
+
+    Args:
+      rule_path: Full rule path.
+
+    Returns:
+      True if the given rule has been resolved and added to the graph.
+    """
+    return self.rule_nodes.get(rule_path, None) != None
+
+  def calculate_rule_sequence(self, target_rule_paths):
+    """Calculates an ordered sequence of rules terminating with the given
+    target rules.
+
+    By passing multiple target names it's possible to build a combined sequence
+    that ensures all the given targets are included with no duplicate
+    dependencies.
+
+    Args:
+      target_rule_paths: A list of target rule paths to include in the
+          sequence, or a single target rule path.
+
+    Returns:
+      An ordered list of Rule instances including all of the given target rules
+      and their dependencies.
+
+    Raises:
+      KeyError: One of the given rules was not found.
+    """
+    if isinstance(target_rule_paths, str):
+      target_rule_paths = [target_rule_paths]
+
+    # Ensure the graph has everything required - if things go south this will
+    # raise errors
+    self._ensure_rules_present(target_rule_paths)
+
+    # Reversed graph to make sorting possible
+    # If this gets expensive (or many sequences are calculated) it could be
+    # cached
+    reverse_graph = self.graph.reverse()
+
+    # Paths are added in reverse (from target to dependencies)
+    sequence_graph = nx.DiGraph()
+
+    def _add_rule_node_dependencies(rule_node):
+      if sequence_graph.has_node(rule_node):
+        # Already present in the sequence graph, no need to add again
+        return
+      # Add node
+      sequence_graph.add_node(rule_node)
+      # Recursively add all dependent children
+      for out_edge in reverse_graph.out_edges_iter(rule_node):
+        out_rule_node = out_edge[1]
+        if not sequence_graph.has_node(out_rule_node):
+          _add_rule_node_dependencies(out_rule_node)
+        sequence_graph.add_edge(rule_node, out_rule_node)
+
+    # Add all paths for targets
+    # Note that all nodes are present if we got this far, so no need to check
+    for rule_path in target_rule_paths:
+      rule = self.project.resolve_rule(rule_path)
+      assert rule
+      rule_node = self.rule_nodes.get(rule.path, None)
+      assert rule_node
+      _add_rule_node_dependencies(rule_node)
+
+    # Reverse the graph so that it's dependencies -> targets
+    reversed_sequence_graph = sequence_graph.reverse()
+
+    # Get the list of nodes in sorted order
+    rule_sequence = []
+    for rule_node in nx.topological_sort(reversed_sequence_graph):
+      rule_sequence.append(rule_node.rule)
+    return rule_sequence
+
+class _RuleNode(object):
+  """A node type that references a rule in the project."""
+
+  def __init__(self, rule):
+    """Initializes a rule node.
+
+    Args:
+      rule: The rule this node describes.
+    """
+    self.rule = rule
+
+  def __repr__(self):
+    return self.rule.path
diff --git a/anvil/graph_test.py b/anvil/graph_test.py
new file mode 100755
index 0000000..b4683f2
--- /dev/null
+++ b/anvil/graph_test.py
@@ -0,0 +1,162 @@
+#!/usr/bin/python
+
+# Copyright 2012 Google Inc. All Rights Reserved.
+
+"""Tests for the graph module.
+"""
+
+__author__ = 'benvanik@google.com (Ben Vanik)'
+
+
+import unittest2
+
+from graph import *
+from module import *
+from rule import *
+from project import *
+
+
+class RuleGraphTest(unittest2.TestCase):
+  """Behavioral tests of the RuleGraph type."""
+
+  def setUp(self):
+    super(RuleGraphTest, self).setUp()
+
+    self.module_1 = Module('m1', rules=[
+        Rule('a1'),
+        Rule('a2'),
+        Rule('a3'),
+        Rule('b', srcs=[':a1', 'a/b/c'], deps=[':a2'],),
+        Rule('c', deps=[':b'],),])
+    self.module_2 = Module('m2', rules=[
+        Rule('p', deps=['m1:c'],)])
+    self.project = Project(modules=[self.module_1, self.module_2])
+
+  def testConstruction(self):
+    project = Project()
+    graph = RuleGraph(project)
+    self.assertIs(graph.project, project)
+
+    project = self.project
+    graph = RuleGraph(project)
+    self.assertIs(graph.project, project)
+
+  def testAddRulesFromModule(self):
+    graph = RuleGraph(self.project)
+    graph.add_rules_from_module(self.module_1)
+    self.assertTrue(graph.has_rule('m1:a1'))
+    self.assertTrue(graph.has_rule('m1:a2'))
+    self.assertTrue(graph.has_rule('m1:a3'))
+    self.assertTrue(graph.has_rule('m1:b'))
+    self.assertTrue(graph.has_rule('m1:c'))
+    self.assertFalse(graph.has_rule('m2:p'))
+    graph.add_rules_from_module(self.module_2)
+    self.assertTrue(graph.has_rule('m2:p'))
+
+    graph = RuleGraph(self.project)
+    graph.add_rules_from_module(self.module_2)
+    self.assertTrue(graph.has_rule('m2:p'))
+    self.assertTrue(graph.has_rule('m1:a1'))
+    self.assertTrue(graph.has_rule('m1:a2'))
+    self.assertFalse(graph.has_rule('m1:a3'))
+    self.assertTrue(graph.has_rule('m1:b'))
+    self.assertTrue(graph.has_rule('m1:c'))
+
+  def testCycle(self):
+    module = Module('mc', rules=[
+        Rule('a', deps=[':b']),
+        Rule('b', deps=[':a'])])
+    project = Project(modules=[module])
+    graph = RuleGraph(project)
+    with self.assertRaises(ValueError):
+      graph.add_rules_from_module(module)
+
+    module_1 = Module('mc1', rules=[Rule('a', deps=['mc2:a'])])
+    module_2 = Module('mc2', rules=[Rule('a', deps=['mc1:a'])])
+    project = Project(modules=[module_1, module_2])
+    graph = RuleGraph(project)
+    with self.assertRaises(ValueError):
+      graph.add_rules_from_module(module_1)
+
+  def testHasRule(self):
+    graph = RuleGraph(self.project)
+    graph.add_rules_from_module(self.module_1)
+    self.assertTrue(graph.has_rule('m1:a1'))
+    self.assertFalse(graph.has_rule('m2:p'))
+    self.assertFalse(graph.has_rule('x:x'))
+
+  def testHasDependency(self):
+    graph = RuleGraph(Project())
+    with self.assertRaises(KeyError):
+      graph.has_dependency('m1:a', 'm1:b')
+
+    graph = RuleGraph(self.project)
+    graph.add_rules_from_module(self.module_1)
+    self.assertTrue(graph.has_dependency('m1:c', 'm1:c'))
+    self.assertTrue(graph.has_dependency('m1:a3', 'm1:a3'))
+    self.assertTrue(graph.has_dependency('m1:c', 'm1:b'))
+    self.assertTrue(graph.has_dependency('m1:c', 'm1:a1'))
+    self.assertTrue(graph.has_dependency('m1:b', 'm1:a1'))
+    self.assertFalse(graph.has_dependency('m1:b', 'm1:c'))
+    self.assertFalse(graph.has_dependency('m1:a1', 'm1:a2'))
+    self.assertFalse(graph.has_dependency('m1:c', 'm1:a3'))
+    with self.assertRaises(KeyError):
+      graph.has_dependency('m1:c', 'm1:x')
+    with self.assertRaises(KeyError):
+      graph.has_dependency('m1:x', 'm1:c')
+    with self.assertRaises(KeyError):
+      graph.has_dependency('m1:x', 'm1:x')
+
+  def testCalculateRuleSequence(self):
+    graph = RuleGraph(self.project)
+
+    with self.assertRaises(KeyError):
+      graph.calculate_rule_sequence(':x')
+    with self.assertRaises(KeyError):
+      graph.calculate_rule_sequence([':x'])
+    with self.assertRaises(KeyError):
+      graph.calculate_rule_sequence(['m1:x'])
+
+    seq = graph.calculate_rule_sequence('m1:a1')
+    self.assertEqual(len(seq), 1)
+    self.assertEqual(seq[0].name, 'a1')
+    seq = graph.calculate_rule_sequence(['m1:a1'])
+    self.assertEqual(len(seq), 1)
+    self.assertEqual(seq[0].name, 'a1')
+
+    seq = graph.calculate_rule_sequence(['m1:b'])
+    self.assertEqual(len(seq), 3)
+    self.assertTrue((seq[0].name in ['a1', 'a2']) or
+                    (seq[1].name in ['a1', 'a2']))
+    self.assertEqual(seq[2].name, 'b')
+
+    seq = graph.calculate_rule_sequence(['m1:a1', 'm1:b'])
+    self.assertEqual(len(seq), 3)
+    self.assertTrue((seq[0].name in ['a1', 'a2']) or
+                    (seq[1].name in ['a1', 'a2']))
+    self.assertEqual(seq[2].name, 'b')
+
+    seq = graph.calculate_rule_sequence(['m1:a1', 'm1:a3'])
+    self.assertEqual(len(seq), 2)
+    self.assertTrue((seq[0].name in ['a1', 'a3']) or
+                    (seq[1].name in ['a1', 'a3']))
+
+    module = Module('mx', rules=[Rule('a', deps=[':b'])])
+    project = Project(modules=[module])
+    graph = RuleGraph(project)
+    with self.assertRaises(KeyError):
+      graph.calculate_rule_sequence('mx:a')
+
+  def testCrossModuleRules(self):
+    graph = RuleGraph(self.project)
+
+    seq = graph.calculate_rule_sequence(['m2:p'])
+    self.assertEqual(len(seq), 5)
+    self.assertTrue((seq[0].name in ['a1', 'a2']) or
+                    (seq[1].name in ['a1', 'a2']))
+    self.assertTrue(seq[4].path, 'm2:p')
+    self.assertTrue(graph.has_dependency('m2:p', 'm1:a1'))
+
+
+if __name__ == '__main__':
+  unittest2.main()
diff --git a/anvil/manage.py b/anvil/manage.py
new file mode 100755
index 0000000..18cc91c
--- /dev/null
+++ b/anvil/manage.py
@@ -0,0 +1,158 @@
+#!/usr/bin/python
+
+# Copyright 2012 Google Inc. All Rights Reserved.
+
+"""Management shell script.
+"""
+
+__author__ = 'benvanik@google.com (Ben Vanik)'
+
+
+import fnmatch
+import imp
+import os
+import sys
+
+import util
+
+
+def _get_anvil_path():
+  """Gets the anvil/ path.
+
+  Returns:
+    The full path to the anvil/ source.
+  """
+  return os.path.normpath(os.path.dirname(__file__))
+
+
+def manage_command(command_name, command_help=None):
+  """A decorator for management command functions.
+  Use this to register management command functions. A function decorated with
+  this will be discovered and callable via manage.py.
+
+  Functions are expected to take (args, cwd) and return an error number that
+  will be passed back to the shell.
+
+  Args:
+    command_name: The name of the command exposed to the management script.
+    command_help: Help text printed alongside the command when queried.
+  """
+  def _exec_command(fn):
+    fn.command_name = command_name
+    fn.command_help = command_help
+    return fn
+  return _exec_command
+
+
+def discover_commands(search_path=None):
+  """Looks for all commands and returns a dictionary of them.
+  Commands are looked for under anvil/commands/, and should be functions
+  decorated with @manage_command.
+
+  Args:
+    search_path: Search path to use instead of the default.
+
+  Returns:
+    A dictionary containing command-to-function mappings.
+
+  Raises:
+    KeyError: Multiple commands have the same name.
+  """
+  commands = {}
+  if not search_path:
+    commands_path = os.path.join(_get_anvil_path(), 'commands')
+  else:
+    commands_path = search_path
+  for (root, dirs, files) in os.walk(commands_path):
+    for name in files:
+      if fnmatch.fnmatch(name, '*.py'):
+        full_path = os.path.join(root, name)
+        module = imp.load_source(os.path.splitext(name)[0], full_path)
+        for attr_name in dir(module):
+          if hasattr(getattr(module, attr_name), 'command_name'):
+            command_fn = getattr(module, attr_name)
+            command_name = command_fn.command_name
+            if commands.has_key(command_name):
+              raise KeyError('Command "%s" already defined' % (command_name))
+            commands[command_name] = command_fn
+  return commands
+
+
+def usage(commands):
+  """Gets usage info that can be displayed to the user.
+
+  Args:
+    commands: A command dictionary from discover_commands.
+
+  Returns:
+    A string containing usage info and a command listing.
+  """
+  s = 'manage.py command [-h]\n'
+  s += '\n'
+  s += 'Commands:\n'
+  for command_name in commands:
+    s += '  %s\n' % (command_name)
+    command_help = commands[command_name].command_help
+    if command_help:
+      s += '    %s\n' % (command_help)
+  return s
+
+
+def run_command(args=None, cwd=None, commands=None):
+  """Runs a command with the given context.
+
+  Args:
+    args: Arguments, with the command to execute as the first.
+    cwd: Current working directory override.
+    commands: A command dictionary from discover_commands to override the
+        defaults.
+
+  Returns:
+    0 if the command succeeded and non-zero otherwise.
+
+  Raises:
+    ValueError: The command could not be found or was not specified.
+  """
+  args = args if args else []
+  cwd = cwd if cwd else os.getcwd()
+
+  commands = commands if commands else discover_commands()
+
+  # TODO(benvanik): look for a .anvilrc, load it to find
+  # - extra command search paths
+  # - extra rule search paths
+  # Also check to see if it was specified in args?
+
+  if not len(args):
+    raise ValueError('No command given')
+  command_name = args[0]
+  if not commands.has_key(command_name):
+    raise ValueError('Command "%s" not found' % (command_name))
+
+  command_fn = commands[command_name]
+  return command_fn(args[1:], cwd)
+
+
+def main(): # pragma: no cover
+  """Entry point for scripts."""
+  # Always add anvil/.. to the path
+  sys.path.insert(1, _get_anvil_path())
+  print sys.path
+  commands = discover_commands()
+
+  try:
+    return_code = run_command(args=sys.argv[1:],
+                              cwd=os.getcwd(),
+                              commands=commands)
+  except ValueError:
+    print usage(commands)
+    return_code = 1
+  except Exception as e:
+    #print e
+    raise
+    return_code = 1
+  sys.exit(return_code)
+
+
+if __name__ == '__main__':
+  main()
diff --git a/anvil/manage_test.py b/anvil/manage_test.py
new file mode 100755
index 0000000..97dadd0
--- /dev/null
+++ b/anvil/manage_test.py
@@ -0,0 +1,66 @@
+#!/usr/bin/python
+
+# Copyright 2012 Google Inc. All Rights Reserved.
+
+"""Tests for the manage module.
+"""
+
+__author__ = 'benvanik@google.com (Ben Vanik)'
+
+
+import types
+import unittest2
+
+import manage
+import test
+from manage import *
+from test import AsyncTestCase, FixtureTestCase
+
+
+class ManageTest(FixtureTestCase):
+  """Behavioral tests for the management wrapper."""
+  fixture = 'manage'
+
+  def testDecorator(self):
+    @manage_command('command_1')
+    def command_1(args, cwd):
+      return 0
+    self.assertEqual(command_1.command_name, 'command_1')
+
+  def testDiscovery(self):
+    # Check built-in
+    commands = manage.discover_commands()
+    self.assertTrue(commands.has_key('build'))
+    self.assertIsInstance(commands['build'], types.FunctionType)
+
+    # Check custom
+    commands = manage.discover_commands(
+        os.path.join(self.root_path, 'commands'))
+    self.assertTrue(commands.has_key('test_command'))
+    self.assertIsInstance(commands['test_command'], types.FunctionType)
+    self.assertEqual(commands['test_command']([], ''), 123)
+
+    # Duplicate command names/etc
+    with self.assertRaises(KeyError):
+      manage.discover_commands(os.path.join(self.root_path, 'bad_commands'))
+
+  def testUsage(self):
+    commands = manage.discover_commands()
+    self.assertNotEqual(len(manage.usage(commands)), 0)
+
+  def testMain(self):
+    with self.assertRaises(ValueError):
+      manage.run_command()
+    with self.assertRaises(ValueError):
+      manage.run_command(['xxx'])
+
+    def some_command(args, cwd):
+      self.assertEqual(len(args), 0)
+      self.assertNotEqual(len(cwd), 0)
+      return 123
+    self.assertEqual(manage.run_command(
+        ['some_command'], commands={'some_command': some_command}), 123)
+
+
+if __name__ == '__main__':
+  unittest2.main()
diff --git a/anvil/module.py b/anvil/module.py
new file mode 100644
index 0000000..908abdc
--- /dev/null
+++ b/anvil/module.py
@@ -0,0 +1,344 @@
+# Copyright 2012 Google Inc. All Rights Reserved.
+
+"""Module representation.
+
+A module is a simple namespace of rules, serving no purpose other than to allow
+for easier organization of projects.
+
+Rules may refer to other rules in the same module with a shorthand (':foo') or
+rules in other modules by specifying a module-relative path
+('stuff/other.py:bar').
+
+TODO(benvanik): details on path resolution
+"""
+
+__author__ = 'benvanik@google.com (Ben Vanik)'
+
+
+import ast
+import glob2
+import io
+import os
+
+import rule
+from rule import RuleNamespace
+
+
+class Module(object):
+  """A rule module.
+  Modules are a flat namespace of rules. The actual resolution of rules occurs
+  later on and is done using all of the modules in a project, allowing for
+  cycles/lazy evaluation/etc.
+  """
+
+  def __init__(self, path, rules=None):
+    """Initializes a module.
+
+    Args:
+      path: A path for the module - should be the path on disk or some other
+          string that is used for referencing.
+      rules: A list of rules to add to the module.
+    """
+    self.path = path
+    self.rules = {}
+    if rules and len(rules):
+      self.add_rules(rules)
+
+  def add_rule(self, rule):
+    """Adds a rule to the module.
+
+    Args:
+      rule: A rule to add. Must have a unique name.
+
+    Raises:
+      KeyError: A rule with the given name already exists in the module.
+    """
+    self.add_rules([rule])
+
+  def add_rules(self, rules):
+    """Adds a list of rules to the module.
+
+    Args:
+      rules: A list of rules to add. Each must have a unique name.
+
+    Raises:
+      KeyError: A rule with the given name already exists in the module.
+    """
+    for rule in rules:
+      if self.rules.get(rule.name, None):
+        raise KeyError('A rule with the name "%s" is already defined' % (
+            rule.name))
+    for rule in rules:
+      self.rules[rule.name] = rule
+      rule.set_parent_module(self)
+
+  def get_rule(self, rule_name):
+    """Gets a rule by name.
+
+    Args:
+      rule_name: Name of the rule to find. May include leading semicolon.
+
+    Returns:
+      The rule with the given name or None if it was not found.
+
+    Raises:
+      NameError: The given rule name was invalid.
+    """
+    if len(rule_name) and rule_name[0] == ':':
+      rule_name = rule_name[1:]
+    if not len(rule_name):
+      raise NameError('Rule name "%s" is invalid' % (rule_name))
+    return self.rules.get(rule_name, None)
+
+  def rule_list(self):
+    """Gets a list of all rules in the module.
+
+    Returns:
+      A list of all rules.
+    """
+    return self.rules.values()
+
+  def rule_iter(self):
+    """Iterates over all rules in the module."""
+    for rule_name in self.rules:
+      yield self.rules[rule_name]
+
+
+class ModuleLoader(object):
+  """A utility type that handles loading modules from files.
+  A loader should only be used to load a single module and then be discarded.
+  """
+
+  def __init__(self, path, rule_namespace=None, modes=None):
+    """Initializes a loader.
+
+    Args:
+      path: File-system path to the module.
+      rule_namespace: Rule namespace to use for rule definitions.
+    """
+    self.path = path
+    self.rule_namespace = rule_namespace
+    if not self.rule_namespace:
+      self.rule_namespace = RuleNamespace()
+      self.rule_namespace.discover()
+    self.modes = {}
+    if modes:
+      for mode in modes:
+        if self.modes.has_key(mode):
+          raise KeyError('Duplicate mode "%s" defined' % (mode))
+        self.modes[mode] = True
+
+    self.code_str = None
+    self.code_ast = None
+    self.code_obj = None
+
+  def load(self, source_string=None):
+    """Loads the module from the given path and prepares it for execution.
+
+    Args:
+      source_string: A string to use as the source. If not provided the file
+          will be loaded at the initialized path.
+
+    Raises:
+      IOError: The file could not be loaded or read.
+      SyntaxError: An error occurred parsing the module.
+    """
+    if self.code_str:
+      raise Exception('ModuleLoader load called multiple times')
+
+    # Read the source as a string
+    if source_string is None:
+      with io.open(self.path, 'r') as f:
+        self.code_str = f.read()
+    else:
+      self.code_str = source_string
+
+    # Parse the AST
+    # This will raise errors if it is not valid
+    self.code_ast = ast.parse(self.code_str, self.path, 'exec')
+
+    # Compile
+    self.code_obj = compile(self.code_ast, self.path, 'exec')
+
+  def execute(self):
+    """Executes the module and returns a Module instance.
+
+    Returns:
+      A new Module instance with all of the rules.
+
+    Raises:
+      NameError: A function or variable name was not found.
+    """
+    all_rules = None
+    rule.begin_capturing_emitted_rules()
+    try:
+      # Setup scope
+      scope = {}
+      self.rule_namespace.populate_scope(scope)
+      self._add_builtins(scope)
+
+      # Execute!
+      exec self.code_obj in scope
+    finally:
+      all_rules = rule.end_capturing_emitted_rules()
+
+    # Gather rules and build the module
+    module = Module(self.path)
+    module.add_rules(all_rules)
+    return module
+
+  def _add_builtins(self, scope):
+    """Adds builtin functions and types to a scope.
+
+    Args:
+      scope: Scope dictionary.
+    """
+    scope['glob'] = self.glob
+    scope['select_one'] = self.select_one
+    scope['select_any'] = self.select_any
+    scope['select_many'] = self.select_many
+
+  def glob(self, expr):
+    """Globs the given expression with the base path of the module.
+    This uses the glob2 module and supports recursive globs ('**/*').
+
+    Args:
+      expr: Glob expression.
+
+    Returns:
+      A list of all files that match the glob expression.
+    """
+    if not expr or not len(expr):
+      return []
+    base_path = os.path.dirname(self.path)
+    glob_path = os.path.join(base_path, expr)
+    return list(glob2.iglob(glob_path))
+
+  def select_one(self, d, default_value):
+    """Selects a single value from the given tuple list based on the current
+    mode settings.
+    This is similar to select_any, only it ensures a reliable ordering in the
+    case of multiple modes being matched.
+
+    If 'A' and 'B' are two non-exclusive modes, then pass
+    [('A', ...), ('B', ...)] to ensure ordering. If only A or B is defined then
+    the respective values will be selected, and if both are defined then the
+    last matching tuple will be returned - in the case of both A and B being
+    defined, the value of 'B'.
+
+    Args:
+      d: A list of (key, value) tuples.
+      default_value: The value to return if nothing matches.
+
+    Returns:
+      A value from the given dictionary based on the current mode, and if none
+      match default_value.
+
+    Raises:
+      KeyError: Multiple keys were matched in the given dictionary.
+    """
+    value = None
+    any_match = False
+    for mode_tuple in d:
+      if self.modes.has_key(mode_tuple[0]):
+        any_match = True
+        value = mode_tuple[1]
+    if not any_match:
+      return default_value
+    return value
+
+  def select_any(self, d, default_value):
+    """Selects a single value from the given dictionary based on the current
+    mode settings.
+    If multiple keys match modes, then a random value will be returned.
+    If you want to ensure consistent return behavior prefer select_one. This is
+    only useful for exclusive modes (such as 'RELEASE' and 'DEBUG').
+
+    For example, if 'DEBUG' and 'RELEASE' are exclusive modes, one can use a
+    dictionary that has 'DEBUG' and 'RELEASE' as keys and if both DEBUG and
+    RELEASE are defined as modes then a KeyError will be raised.
+
+    Args:
+      d: Dictionary of mode key-value pairs.
+      default_value: The value to return if nothing matches.
+
+    Returns:
+      A value from the given dictionary based on the current mode, and if none
+      match default_value.
+
+    Raises:
+      KeyError: Multiple keys were matched in the given dictionary.
+    """
+    value = None
+    any_match = False
+    for mode in d:
+      if self.modes.has_key(mode):
+        if any_match:
+          raise KeyError(
+              'Multiple modes match in the given dictionary - use select_one '
+              'instead to ensure ordering')
+        any_match = True
+        value = d[mode]
+    if not any_match:
+      return default_value
+    return value
+
+  def select_many(self, d, default_value):
+    """Selects as many values from the given dictionary as match the current
+    mode settings.
+
+    This expects the values of the keys in the dictionary to be uniform (for
+    example, all lists, dictionaries, or primitives). If any do not match a
+    TypeError is thrown.
+
+    If values are dictionaries then the result will be a dictionary that is
+    an aggregate of all matching values. If the values are lists then a single
+    combined list is returned. All other types are placed into a list that is
+    returned.
+
+    Args:
+      d: Dictionary of mode key-value pairs.
+      default_value: The value to return if nothing matches.
+
+    Returns:
+      A list or dictionary of combined values that match any modes, or the
+      default_value.
+
+    Raises:
+      TypeError: The type of a value does not match the expected type.
+    """
+    if isinstance(default_value, list):
+      results = []
+    elif isinstance(default_value, dict):
+      results = {}
+    else:
+      results = []
+    any_match = False
+    for mode in d:
+      if self.modes.has_key(mode):
+        any_match = True
+        mode_value = d[mode]
+        if isinstance(mode_value, list):
+          if type(mode_value) != type(default_value):
+            raise TypeError('Type mismatch in dictionary (expected list)')
+          results.extend(mode_value)
+        elif isinstance(mode_value, dict):
+          if type(mode_value) != type(default_value):
+            raise TypeError('Type mismatch in dictionary (expected dict)')
+          results.update(mode_value)
+        else:
+          if type(default_value) == list:
+            raise TypeError('Type mismatch in dictionary (expected list)')
+          elif type(default_value) == dict:
+            raise TypeError('Type mismatch in dictionary (expected dict)')
+          results.append(mode_value)
+    if not any_match:
+      if default_value is None:
+        return None
+      elif isinstance(default_value, list):
+        results.extend(default_value)
+      elif isinstance(default_value, dict):
+        results.update(default_value)
+      else:
+        results.append(default_value)
+    return results
diff --git a/anvil/module_test.py b/anvil/module_test.py
new file mode 100755
index 0000000..fa00ca3
--- /dev/null
+++ b/anvil/module_test.py
@@ -0,0 +1,414 @@
+#!/usr/bin/python
+
+# Copyright 2012 Google Inc. All Rights Reserved.
+
+"""Tests for the module module.
+"""
+
+__author__ = 'benvanik@google.com (Ben Vanik)'
+
+
+import glob2
+import os
+import unittest2
+
+from module import *
+from rule import *
+from test import FixtureTestCase
+
+
+class ModuleTest(unittest2.TestCase):
+  """Behavioral tests of Module rule handling."""
+
+  def testEmptyModule(self):
+    module = Module('m')
+    self.assertIsNone(module.get_rule(':a'))
+    self.assertEqual(len(module.rule_list()), 0)
+    self.assertEqual(len(list(module.rule_iter())), 0)
+
+  def testModulePath(self):
+    module = Module('a')
+    self.assertEqual(module.path, 'a')
+
+  def testModuleRuleInit(self):
+    rule_a = Rule('a')
+    rule_b = Rule('b')
+    rule_list = [rule_a, rule_b]
+    module = Module('m', rules=rule_list)
+    self.assertIsNot(module.rule_list(), rule_list)
+    self.assertEqual(len(module.rule_list()), len(rule_list))
+    self.assertIs(module.get_rule(':a'), rule_a)
+    self.assertIs(module.get_rule(':b'), rule_b)
+
+  def testAddRule(self):
+    rule_a = Rule('a')
+    rule_b = Rule('b')
+
+    module = Module('m')
+    self.assertIsNone(module.get_rule(':a'))
+
+    module.add_rule(rule_a)
+    self.assertIs(module.get_rule('a'), rule_a)
+    self.assertIs(module.get_rule(':a'), rule_a)
+    self.assertEqual(len(module.rule_list()), 1)
+    self.assertEqual(len(list(module.rule_iter())), 1)
+    self.assertIs(module.rule_list()[0], rule_a)
+    self.assertEqual(list(module.rule_iter())[0], rule_a)
+    self.assertIsNone(module.get_rule(':b'))
+
+    module.add_rule(rule_b)
+    self.assertIs(module.get_rule(':b'), rule_b)
+    self.assertEqual(len(module.rule_list()), 2)
+    self.assertEqual(len(list(module.rule_iter())), 2)
+
+    with self.assertRaises(KeyError):
+      module.add_rule(rule_b)
+    self.assertEqual(len(module.rule_list()), 2)
+
+  def testAddRules(self):
+    rule_a = Rule('a')
+    rule_b = Rule('b')
+    rule_list = [rule_a, rule_b]
+
+    module = Module('m')
+    self.assertIsNone(module.get_rule('a'))
+    self.assertIsNone(module.get_rule(':a'))
+    self.assertIsNone(module.get_rule('b'))
+    self.assertIsNone(module.get_rule(':b'))
+    self.assertEqual(len(module.rule_list()), 0)
+
+    module.add_rules(rule_list)
+    self.assertEqual(len(module.rule_list()), 2)
+    self.assertEqual(len(list(module.rule_iter())), 2)
+    self.assertIsNot(module.rule_list(), rule_list)
+    self.assertIs(module.get_rule(':a'), rule_a)
+    self.assertIs(module.get_rule(':b'), rule_b)
+
+    with self.assertRaises(KeyError):
+      module.add_rule(rule_b)
+    self.assertEqual(len(module.rule_list()), 2)
+    with self.assertRaises(KeyError):
+      module.add_rules([rule_b])
+    self.assertEqual(len(module.rule_list()), 2)
+    with self.assertRaises(KeyError):
+      module.add_rules(rule_list)
+    self.assertEqual(len(module.rule_list()), 2)
+
+  def testGetRule(self):
+    rule = Rule('a')
+    module = Module('m')
+    module.add_rule(rule)
+
+    self.assertIs(module.get_rule('a'), rule)
+    self.assertIs(module.get_rule(':a'), rule)
+
+    self.assertIsNone(module.get_rule(':x'))
+
+    with self.assertRaises(NameError):
+      module.get_rule('')
+    with self.assertRaises(NameError):
+      module.get_rule(':')
+
+  def testRuleParentModule(self):
+    rule_a = Rule('a')
+    module = Module('m')
+
+    self.assertIsNone(rule_a.parent_module)
+    self.assertEqual(rule_a.path, ':a')
+
+    module.add_rule(rule_a)
+
+    self.assertIs(rule_a.parent_module, module)
+    self.assertEqual(rule_a.path, 'm:a')
+
+    with self.assertRaises(ValueError):
+      rule_a.set_parent_module(module)
+
+
+class ModuleLoaderTest(FixtureTestCase):
+  """Behavioral tests for ModuleLoader."""
+  fixture = 'simple'
+
+  def testModes(self):
+    module_path = os.path.join(self.temp_path, 'simple', 'BUILD')
+
+    loader = ModuleLoader(module_path)
+    self.assertEqual(len(loader.modes), 0)
+    loader = ModuleLoader(module_path, modes=None)
+    self.assertEqual(len(loader.modes), 0)
+    loader = ModuleLoader(module_path, modes=[])
+    self.assertEqual(len(loader.modes), 0)
+    loader = ModuleLoader(module_path, modes=['A'])
+    self.assertEqual(len(loader.modes), 1)
+    modes = ['A', 'B']
+    loader = ModuleLoader(module_path, modes=modes)
+    self.assertIsNot(loader.modes, modes)
+    self.assertEqual(len(loader.modes), 2)
+
+    with self.assertRaises(KeyError):
+      ModuleLoader(module_path, modes=['A', 'A'])
+
+  def testLoad(self):
+    module_path = os.path.join(self.temp_path, 'simple', 'BUILD')
+    loader = ModuleLoader(module_path)
+    loader.load()
+
+    loader = ModuleLoader(module_path + '.not-real')
+    with self.assertRaises(IOError):
+      loader.load()
+
+    loader = ModuleLoader(module_path)
+    loader.load(source_string='x = 5')
+    with self.assertRaises(Exception):
+      loader.load(source_string='y = 5')
+
+    loader = ModuleLoader(module_path)
+    with self.assertRaises(SyntaxError):
+      loader.load(source_string='x/')
+    with self.assertRaises(Exception):
+      loader.load(source_string='y = 5')
+
+  def testExecute(self):
+    module_path = os.path.join(self.temp_path, 'simple', 'BUILD')
+
+    loader = ModuleLoader(module_path)
+    loader.load(source_string='asdf()')
+    with self.assertRaises(NameError):
+      loader.execute()
+
+    loader = ModuleLoader(module_path)
+    loader.load(source_string='')
+    module = loader.execute()
+    self.assertEqual(len(module.rule_list()), 0)
+
+    loader = ModuleLoader(module_path)
+    loader.load(source_string='x = 5')
+    module = loader.execute()
+    self.assertEqual(len(module.rule_list()), 0)
+
+    loader = ModuleLoader(module_path)
+    loader.load(source_string='file_set("a")\nfile_set("b")')
+    module = loader.execute()
+    self.assertEqual(len(module.rule_list()), 2)
+    self.assertIsNotNone(module.get_rule(':a'))
+    self.assertIsNotNone(module.get_rule(':b'))
+    self.assertEqual(module.get_rule(':a').name, 'a')
+    self.assertEqual(module.get_rule(':b').name, 'b')
+
+  def testBuiltins(self):
+    module_path = os.path.join(self.temp_path, 'simple', 'BUILD')
+
+    loader = ModuleLoader(module_path, modes=['A'])
+    loader.load(source_string=(
+        'file_set("a", srcs=select_any({"A": "sa"}, "sx"))\n'
+        'file_set("b", srcs=select_any({"B": "sb"}, "sx"))\n'
+        'file_set("c", srcs=select_one([("A", "sa")], "sx"))\n'
+        'file_set("d", srcs=select_many({"B": "sb"}, "sx"))\n'))
+    module = loader.execute()
+    self.assertEqual(module.get_rule(':a').srcs[0], 'sa')
+    self.assertEqual(module.get_rule(':b').srcs[0], 'sx')
+    self.assertEqual(module.get_rule(':c').srcs[0], 'sa')
+    self.assertEqual(module.get_rule(':d').srcs[0], 'sx')
+
+  def testCustomRules(self):
+    module_path = os.path.join(self.temp_path, 'simple', 'BUILD')
+
+    class MockRule1(Rule):
+      pass
+    rule_namespace = RuleNamespace()
+    rule_namespace.add_rule_type('mock_rule_1', MockRule1)
+    loader = ModuleLoader(module_path, rule_namespace=rule_namespace)
+    loader.load(source_string='mock_rule_1("a")')
+    module = loader.execute()
+    self.assertEqual(len(module.rule_list()), 1)
+    self.assertIsNotNone(module.get_rule(':a'))
+    self.assertEqual(module.get_rule(':a').name, 'a')
+
+  def testGlob(self):
+    module_path = os.path.join(self.temp_path, 'simple', 'BUILD')
+
+    loader = ModuleLoader(module_path)
+    loader.load(source_string='file_set("a", srcs=glob(""))')
+    module = loader.execute()
+    self.assertEqual(len(module.rule_list()), 1)
+    self.assertIsNotNone(module.get_rule(':a'))
+    rule = module.get_rule(':a')
+    self.assertEqual(len(rule.srcs), 0)
+
+    loader = ModuleLoader(module_path)
+    loader.load(source_string='file_set("a", srcs=glob("*.txt"))')
+    module = loader.execute()
+    self.assertEqual(len(module.rule_list()), 1)
+    self.assertIsNotNone(module.get_rule(':a'))
+    rule = module.get_rule(':a')
+    self.assertEqual(len(rule.srcs), 3)
+
+    loader = ModuleLoader(module_path)
+    loader.load(source_string='file_set("a", srcs=glob("**/*.txt"))')
+    module = loader.execute()
+    self.assertEqual(len(module.rule_list()), 1)
+    self.assertIsNotNone(module.get_rule(':a'))
+    rule = module.get_rule(':a')
+    self.assertEqual(len(rule.srcs), 5)
+
+    loader = ModuleLoader(module_path)
+    loader.load(source_string='file_set("a", srcs=glob("a.txt"))')
+    module = loader.execute()
+    self.assertEqual(len(module.rule_list()), 1)
+    self.assertIsNotNone(module.get_rule(':a'))
+    rule = module.get_rule(':a')
+    self.assertEqual(len(rule.srcs), 1)
+
+    loader = ModuleLoader(module_path)
+    loader.load(source_string='file_set("a", srcs=glob("x.txt"))')
+    module = loader.execute()
+    self.assertEqual(len(module.rule_list()), 1)
+    self.assertIsNotNone(module.get_rule(':a'))
+    rule = module.get_rule(':a')
+    self.assertEqual(len(rule.srcs), 0)
+
+    loader = ModuleLoader(module_path)
+    loader.load(source_string='file_set("a", srcs=glob("*.notpresent"))')
+    module = loader.execute()
+    self.assertEqual(len(module.rule_list()), 1)
+    self.assertIsNotNone(module.get_rule(':a'))
+    rule = module.get_rule(':a')
+    self.assertEqual(len(rule.srcs), 0)
+
+
+class ModuleLoaderSelectionTest(unittest2.TestCase):
+  """Behavioral tests for ModuleLoader selection utilities."""
+
+  def testSelectOne(self):
+    loader = ModuleLoader('some/path')
+    self.assertEqual(loader.select_one([
+        ], default_value=100), 100)
+    self.assertEqual(loader.select_one([
+        ('A', 1),
+        ('B', 2),
+        ], default_value=100), 100)
+
+    loader = ModuleLoader('some/path', modes=['A', 'B', 'C'])
+    self.assertEqual(loader.select_one([
+        ('X', 99),
+        ], default_value=100), 100)
+    self.assertEqual(loader.select_one([
+        ('A', 1),
+        ], default_value=100), 1)
+    self.assertEqual(loader.select_one([
+        ('A', 1),
+        ('B', 2),
+        ], default_value=100), 2)
+    self.assertEqual(loader.select_one([
+        ('B', 2),
+        ('A', 1),
+        ], default_value=100), 1)
+
+  def testSelectAny(self):
+    loader = ModuleLoader('some/path')
+    self.assertEqual(loader.select_any({
+        }, default_value=100), 100)
+    self.assertIsNone(loader.select_any({
+        'A': 1,
+        'B': 2,
+        }, default_value=None))
+    self.assertEqual(loader.select_any({
+        'A': 1,
+        'B': 2,
+        }, default_value=100), 100)
+
+    loader = ModuleLoader('some/path', modes=['A', 'B', 'C'])
+    self.assertEqual(loader.select_any({
+        }, default_value=100), 100)
+    self.assertEqual(loader.select_any({
+        'X': 99,
+        }, default_value=100), 100)
+    self.assertEqual(loader.select_any({
+        'X': 99,
+        'A': 1,
+        }, default_value=100), 1)
+    self.assertEqual(loader.select_any({
+        'X': 99,
+        'B': 2,
+        }, default_value=100), 2)
+
+    with self.assertRaises(KeyError):
+      loader.select_any({
+          'A': 1,
+          'B': 2,
+          }, default_value=100)
+
+  def testSelectMany(self):
+    loader = ModuleLoader('some/path')
+    self.assertIsNone(loader.select_many({}, default_value=None))
+    self.assertEqual(loader.select_many({}, default_value=[]), [])
+    self.assertEqual(loader.select_many({}, default_value=[1]), [1])
+    self.assertEqual(loader.select_many({}, default_value={}), {})
+    self.assertEqual(loader.select_many({}, default_value={'a': 1}), {'a': 1})
+    self.assertEqual(loader.select_many({}, default_value=1), [1])
+    self.assertEqual(loader.select_many({}, default_value='a'), ['a'])
+    self.assertEqual(loader.select_many({
+        'A': 1,
+        }, default_value=100), [100])
+    self.assertEqual(loader.select_many({
+        'A': [1, 2, 3],
+        }, default_value=[100, 101, 102]), [100, 101, 102])
+    self.assertEqual(loader.select_many({
+        'A': {'a': 1},
+        }, default_value={'d': 100}), {'d': 100})
+
+    loader = ModuleLoader('some/path', modes=['A', 'B', 'C'])
+    self.assertEqual(loader.select_many({}, default_value=[]), [])
+    self.assertEqual(loader.select_many({
+        'X': 1,
+        }, default_value=100), [100])
+    self.assertEqual(loader.select_many({
+        'A': 1,
+        }, default_value=100), [1])
+    self.assertEqual(loader.select_many({
+        'A': 1,
+        'B': 2,
+        }, default_value=100), [1, 2])
+    self.assertEqual(loader.select_many({
+        'A': [1, 2, 3],
+        }, default_value=[100]), [1, 2, 3])
+    self.assertEqual(loader.select_many({
+        'A': [1, 2, 3],
+        'B': [4, 5, 6],
+        }, default_value=[100]), [1, 2, 3, 4, 5, 6])
+    self.assertEqual(loader.select_many({
+        'A': {'a': 1},
+        }, default_value={'d': 100}), {'a': 1})
+    self.assertEqual(loader.select_many({
+        'A': {'a': 1},
+        'B': {'b': 2},
+        }, default_value={'d': 100}), {'a': 1, 'b': 2})
+
+    with self.assertRaises(TypeError):
+      loader.select_many({
+          'A': 1,
+          }, default_value=[100])
+    with self.assertRaises(TypeError):
+      loader.select_many({
+          'A': 1,
+          }, default_value={'d': 100})
+    with self.assertRaises(TypeError):
+      loader.select_many({
+          'A': [1],
+          }, default_value=100)
+    with self.assertRaises(TypeError):
+      loader.select_many({
+          'A': [1],
+          }, default_value={'d': 100})
+    with self.assertRaises(TypeError):
+      loader.select_many({
+          'A': {'a': 1},
+          }, default_value=100)
+    with self.assertRaises(TypeError):
+      loader.select_many({
+          'A': {'a': 1},
+          }, default_value=[100])
+
+
+if __name__ == '__main__':
+  unittest2.main()
diff --git a/anvil/project.py b/anvil/project.py
new file mode 100644
index 0000000..43ebe76
--- /dev/null
+++ b/anvil/project.py
@@ -0,0 +1,283 @@
+# Copyright 2012 Google Inc. All Rights Reserved.
+
+"""Project representation.
+
+A project is a module (or set of modules) that provides a namespace of rules.
+Rules may refer to each other and will be resolved in the project namespace.
+"""
+
+__author__ = 'benvanik@google.com (Ben Vanik)'
+
+
+import base64
+import os
+import pickle
+import re
+import stat
+import string
+
+from module import ModuleLoader
+from rule import RuleNamespace
+import util
+
+
+class Project(object):
+  """Project type that contains rules.
+  Projects, once constructed, are designed to be immutable. Many duplicate
+  build processes may run over the same project instance and all expect it to
+  be in the state it was when first created.
+  """
+
+  def __init__(self, name='Project', rule_namespace=None, module_resolver=None,
+               modules=None):
+    """Initializes an empty project.
+
+    Args:
+      name: A human-readable name for the project that will be used for
+          logging.
+      rule_namespace: Rule namespace to use when loading modules. If omitted a
+          default one is used.
+      module_resolver: A module resolver to use when attempt to dynamically
+          resolve modules by path.
+      modules: A list of modules to add to the project.
+
+    Raises:
+      NameError: The name given is not valid.
+    """
+    self.name = name
+
+    if rule_namespace:
+      self.rule_namespace = rule_namespace
+    else:
+      self.rule_namespace = RuleNamespace()
+      self.rule_namespace.discover()
+
+    if module_resolver:
+      self.module_resolver = module_resolver
+    else:
+      self.module_resolver = StaticModuleResolver()
+
+    self.modules = {}
+    if modules and len(modules):
+      self.add_modules(modules)
+
+  def add_module(self, module):
+    """Adds a module to the project.
+
+    Args:
+      module: A module to add.
+
+    Raises:
+      KeyError: A module with the given name already exists in the project.
+    """
+    self.add_modules([module])
+
+  def add_modules(self, modules):
+    """Adds a list of modules to the project.
+
+    Args:
+      modules: A list of modules to add.
+
+    Raises:
+      KeyError: A module with the given name already exists in the project.
+    """
+    for module in modules:
+      if self.modules.get(module.path, None):
+        raise KeyError('A module with the path "%s" is already defined' % (
+            module.path))
+    for module in modules:
+      self.modules[module.path] = module
+
+  def get_module(self, module_path):
+    """Gets a module by path.
+
+    Args:
+      module_path: Name of the module to find.
+
+    Returns:
+      The module with the given path or None if it was not found.
+    """
+    return self.modules.get(module_path, None)
+
+  def module_list(self):
+    """Gets a list of all modules in the project.
+
+    Returns:
+      A list of all modules.
+    """
+    return self.modules.values()
+
+  def module_iter(self):
+    """Iterates over all modules in the project."""
+    for module_path in self.modules:
+      yield self.modules[module_path]
+
+  def resolve_rule(self, rule_path, requesting_module=None):
+    """Gets a rule by path, supporting module lookup and dynamic loading.
+
+    Args:
+      rule_path: Path of the rule to find. Must include a semicolon.
+      requesting_module: The module that is requesting the given rule. If not
+          provided then no local rule paths (':foo') or relative paths are
+          allowed.
+
+    Returns:
+      The rule with the given name or None if it was not found.
+
+    Raises:
+      NameError: The given rule name was not valid.
+      KeyError: The given rule was not found.
+    """
+    if string.find(rule_path, ':') == -1:
+      raise NameError('The rule path "%s" is missing a semicolon' % (rule_path))
+    (module_path, rule_name) = string.rsplit(rule_path, ':', 1)
+    if self.module_resolver.can_resolve_local:
+      if not len(module_path) and not requesting_module:
+        module_path = '.'
+    if not len(module_path) and not requesting_module:
+      raise KeyError('Local rule "%s" given when no resolver defined' % (
+          rule_path))
+
+    module = requesting_module
+    if len(module_path):
+      requesting_path = None
+      if requesting_module:
+        requesting_path = os.path.dirname(requesting_module.path)
+      full_path = self.module_resolver.resolve_module_path(
+          module_path, requesting_path)
+      module = self.modules.get(full_path, None)
+      if not module:
+        # Module not yet loaded - need to grab it
+        module = self.module_resolver.load_module(
+            full_path, self.rule_namespace)
+        if module:
+          self.add_module(module)
+        else:
+          raise IOError('Module "%s" not found', module_path)
+
+    return module.get_rule(rule_name)
+
+
+class ModuleResolver(object):
+  """A type to use for resolving modules.
+  This is used to get a module when a project tries to resolve a rule in a
+  module that has not yet been loaded.
+  """
+
+  def __init__(self, *args, **kwargs):
+    """Initializes a module resolver."""
+    self.can_resolve_local = False
+
+  def resolve_module_path(self, path, working_path=None):
+    """Resolves a module path to its full, absolute path.
+    This is used by the project system to disambugate modules and check the
+    cache before actually performing a load.
+    The path returned from this will be passed to load_module.
+
+    Args:
+      path: Path of the module (may be relative/etc).
+      working_path: Path relative paths should be pased off of. If not provided
+          then relative paths may fail.
+
+    Returns:
+      An absolute path that can be used as a cache key and passed to
+      load_module.
+    """
+    raise NotImplementedError()
+
+  def load_module(self, full_path, rule_namespace):
+    """Loads a module from the given path.
+
+    Args:
+      full_path: Absolute path of the module as returned by resolve_module_path.
+      rule_namespace: Rule namespace to use when loading modules.
+
+    Returns:
+      A Module representing the given path or None if it could not be found.
+
+    Raises:
+      IOError/OSError: The module could not be found.
+    """
+    raise NotImplementedError()
+
+
+class StaticModuleResolver(ModuleResolver):
+  """A static module resolver that can resolve from a list of modules.
+  """
+
+  def __init__(self, modules=None, *args, **kwargs):
+    """Initializes a static module resolver.
+
+    Args:
+      modules: A list of modules that can be resolved.
+    """
+    super(StaticModuleResolver, self).__init__(*args, **kwargs)
+
+    self.modules = {}
+    if modules:
+      for module in modules:
+        self.modules[module.path] = module
+
+  def resolve_module_path(self, path, working_path=None):
+    real_path = path
+    if working_path and len(working_path):
+      real_path = os.path.join(working_path, path)
+    return os.path.normpath(real_path)
+
+  def load_module(self, full_path, rule_namespace):
+    return self.modules.get(full_path, None)
+
+
+class FileModuleResolver(ModuleResolver):
+  """A file-system backed module resolver.
+
+  Rules are searched for with relative paths from a defined root path.
+  If the module path given is a directory, the resolver will attempt to load
+  a BUILD file from that directory - otherwise the file specified will be
+  treated as the module.
+  """
+
+  def __init__(self, root_path, *args, **kwargs):
+    """Initializes a file-system module resolver.
+
+    Args:
+      root_path: Root filesystem path to treat as the base for all resolutions.
+
+    Raises:
+      IOError: The given root path is not found or is not a directory.
+    """
+    super(FileModuleResolver, self).__init__(*args, **kwargs)
+
+    self.can_resolve_local = True
+
+    self.root_path = root_path
+    if not os.path.isdir(root_path):
+      raise IOError('Root path "%s" not found' % (root_path))
+
+  def resolve_module_path(self, path, working_path=None):
+    # Compute the real path
+    has_working_path = working_path and len(working_path)
+    real_path = path
+    if has_working_path:
+      real_path = os.path.join(working_path, path)
+    real_path = os.path.normpath(real_path)
+    full_path = os.path.join(self.root_path, real_path)
+
+    # Check to see if it exists and is a file
+    # Special handling to find BUILD files under directories
+    mode = os.stat(full_path).st_mode
+    if stat.S_ISDIR(mode):
+      full_path = os.path.join(full_path, 'BUILD')
+      if not os.path.isfile(full_path):
+        raise IOError('Path "%s" is not a file' % (full_path))
+    elif stat.S_ISREG(mode):
+      pass
+    else:
+      raise IOError('Path "%s" is not a file' % (full_path))
+
+    return os.path.normpath(full_path)
+
+  def load_module(self, full_path, rule_namespace):
+    module_loader = ModuleLoader(full_path, rule_namespace=rule_namespace)
+    module_loader.load()
+    return module_loader.execute()
diff --git a/anvil/project_test.py b/anvil/project_test.py
new file mode 100755
index 0000000..36145ad
--- /dev/null
+++ b/anvil/project_test.py
@@ -0,0 +1,323 @@
+#!/usr/bin/python
+
+# Copyright 2012 Google Inc. All Rights Reserved.
+
+"""Tests for the project module.
+"""
+
+__author__ = 'benvanik@google.com (Ben Vanik)'
+
+
+import os
+import unittest2
+
+from module import *
+from rule import *
+from project import *
+from test import FixtureTestCase
+
+
+class ProjectTest(unittest2.TestCase):
+  """Behavioral tests of Project rule handling."""
+
+  def testEmptyProject(self):
+    project = Project()
+    self.assertIsNone(project.get_module(':a'))
+    self.assertEqual(len(project.module_list()), 0)
+    self.assertEqual(len(list(project.module_iter())), 0)
+
+  def testProjectName(self):
+    project = Project()
+    self.assertNotEqual(len(project.name), 0)
+    project = Project(name='a')
+    self.assertEqual(project.name, 'a')
+
+  def testProjectRuleNamespace(self):
+    project = Project()
+    self.assertIsNotNone(project.rule_namespace)
+    rule_namespace = RuleNamespace()
+    project = Project(rule_namespace=rule_namespace)
+    self.assertIs(project.rule_namespace, rule_namespace)
+
+  def testProjectModuleInit(self):
+    module_a = Module('ma', rules=[Rule('a')])
+    module_b = Module('mb', rules=[Rule('b')])
+    module_list = [module_a, module_b]
+    project = Project(modules=module_list)
+    self.assertIsNot(project.module_list(), module_list)
+    self.assertEqual(len(project.module_list()), len(module_list))
+    self.assertIs(project.get_module('ma'), module_a)
+    self.assertIs(project.get_module('mb'), module_b)
+
+  def testAddModule(self):
+    module_a = Module('ma', rules=[Rule('a')])
+    module_b = Module('mb', rules=[Rule('b')])
+
+    project = Project()
+    self.assertIsNone(project.get_module('ma'))
+    self.assertIsNone(project.get_module('mb'))
+    self.assertEqual(len(project.module_list()), 0)
+
+    project.add_module(module_a)
+    self.assertIs(project.get_module('ma'), module_a)
+    self.assertEqual(len(project.module_list()), 1)
+    self.assertEqual(len(list(project.module_iter())), 1)
+    self.assertEqual(project.module_list()[0], module_a)
+    self.assertEqual(list(project.module_iter())[0], module_a)
+    self.assertIsNone(project.get_module('mb'))
+
+    project.add_module(module_b)
+    self.assertIs(project.get_module('mb'), module_b)
+    self.assertEqual(len(project.module_list()), 2)
+    self.assertEqual(len(list(project.module_iter())), 2)
+
+    with self.assertRaises(KeyError):
+      project.add_module(module_b)
+    self.assertEqual(len(project.module_list()), 2)
+
+  def testAddModules(self):
+    module_a = Module('ma', rules=[Rule('a')])
+    module_b = Module('mb', rules=[Rule('b')])
+    module_list = [module_a, module_b]
+
+    project = Project()
+    self.assertIsNone(project.get_module('ma'))
+    self.assertIsNone(project.get_module('mb'))
+    self.assertEqual(len(project.module_list()), 0)
+
+    project.add_modules(module_list)
+    self.assertIsNot(project.module_list(), module_list)
+    self.assertEqual(len(project.module_list()), len(module_list))
+    self.assertIs(project.get_module('ma'), module_a)
+    self.assertIs(project.get_module('mb'), module_b)
+
+    with self.assertRaises(KeyError):
+      project.add_module(module_b)
+    self.assertEqual(len(project.module_list()), len(module_list))
+    with self.assertRaises(KeyError):
+      project.add_modules([module_b])
+    self.assertEqual(len(project.module_list()), len(module_list))
+    with self.assertRaises(KeyError):
+      project.add_modules(module_list)
+    self.assertEqual(len(project.module_list()), len(module_list))
+
+  def testGetModule(self):
+    module_a = Module('ma', rules=[Rule('a')])
+    module_b = Module('mb', rules=[Rule('b')])
+    project = Project(modules=[module_a, module_b])
+
+    self.assertIs(project.get_module('ma'), module_a)
+    self.assertIs(project.get_module('mb'), module_b)
+    self.assertIsNone(project.get_module('mx'))
+
+  def testResolveRule(self):
+    rule_a = Rule('a')
+    rule_b = Rule('b')
+    module_a = Module('ma', rules=[rule_a])
+    module_b = Module('mb', rules=[rule_b])
+    project = Project(modules=[module_a, module_b])
+
+    with self.assertRaises(NameError):
+      project.resolve_rule('')
+    with self.assertRaises(NameError):
+      project.resolve_rule('a')
+    with self.assertRaises(NameError):
+      project.resolve_rule('a/b/c')
+    with self.assertRaises(NameError):
+      project.resolve_rule('a', requesting_module=module_a)
+
+    self.assertIs(project.resolve_rule(':a', requesting_module=module_a),
+                  rule_a)
+    self.assertIs(project.resolve_rule(':b', requesting_module=module_b),
+                  rule_b)
+    self.assertIs(project.resolve_rule('ma:a', requesting_module=module_a),
+                  rule_a)
+    self.assertIs(project.resolve_rule('mb:b', requesting_module=module_b),
+                  rule_b)
+    self.assertIs(project.resolve_rule('mb:b', requesting_module=module_a),
+                  rule_b)
+    self.assertIs(project.resolve_rule('ma:a', requesting_module=module_b),
+                  rule_a)
+
+  def testModuleResolver(self):
+    rule_a = Rule('a')
+    rule_b = Rule('b')
+    module_a = Module('ma', rules=[rule_a])
+    module_b = Module('mb', rules=[rule_b])
+    module_resolver = StaticModuleResolver([module_a, module_b])
+    project = Project(module_resolver=module_resolver)
+
+    self.assertEqual(len(project.module_list()), 0)
+    self.assertIs(project.resolve_rule('ma:a'), rule_a)
+    self.assertEqual(len(project.module_list()), 1)
+    self.assertIs(project.resolve_rule('mb:b'), rule_b)
+    self.assertEqual(len(project.module_list()), 2)
+
+    with self.assertRaises(IOError):
+      project.resolve_rule('mx:x')
+
+  def testRelativeModuleResolver(self):
+    rule_a = Rule('a')
+    rule_b = Rule('b')
+    module_a = Module('ma', rules=[rule_a])
+    module_b = Module('b/mb', rules=[rule_b])
+    module_resolver = StaticModuleResolver([module_a, module_b])
+    project = Project(module_resolver=module_resolver)
+
+    self.assertEqual(len(project.module_list()), 0)
+    with self.assertRaises(IOError):
+        project.resolve_rule('ma:a', requesting_module=module_b)
+    self.assertIs(project.resolve_rule('../ma:a',
+                                       requesting_module=module_b), rule_a)
+    self.assertIs(project.resolve_rule('b/mb:b',
+                                       requesting_module=module_a), rule_b)
+
+
+class FileModuleResolverTest(FixtureTestCase):
+  """Behavioral tests for FileModuleResolver."""
+  fixture = 'resolution'
+
+  def testResolverInit(self):
+    FileModuleResolver(self.root_path)
+
+    with self.assertRaises(IOError):
+      FileModuleResolver(os.path.join(self.root_path, 'x'))
+
+  def testResolveModulePath(self):
+    module_resolver = FileModuleResolver(self.root_path)
+
+    self.assertEqual(module_resolver.resolve_module_path('BUILD'),
+                     os.path.join(self.root_path, 'BUILD'))
+    self.assertEqual(module_resolver.resolve_module_path('./BUILD'),
+                     os.path.join(self.root_path, 'BUILD'))
+    self.assertEqual(module_resolver.resolve_module_path('.'),
+                     os.path.join(self.root_path, 'BUILD'))
+    self.assertEqual(module_resolver.resolve_module_path('./a/..'),
+                     os.path.join(self.root_path, 'BUILD'))
+    self.assertEqual(module_resolver.resolve_module_path('./a/../BUILD'),
+                     os.path.join(self.root_path, 'BUILD'))
+
+    self.assertEqual(module_resolver.resolve_module_path('BUILD', 'a'),
+                     os.path.join(self.root_path, 'a', 'BUILD'))
+    self.assertEqual(module_resolver.resolve_module_path('.', 'a'),
+                     os.path.join(self.root_path, 'a', 'BUILD'))
+    self.assertEqual(module_resolver.resolve_module_path('..', 'a'),
+                     os.path.join(self.root_path, 'BUILD'))
+    self.assertEqual(module_resolver.resolve_module_path('../.', 'a'),
+                     os.path.join(self.root_path, 'BUILD'))
+    self.assertEqual(module_resolver.resolve_module_path('../BUILD', 'a'),
+                     os.path.join(self.root_path, 'BUILD'))
+
+    with self.assertRaises(IOError):
+      module_resolver.resolve_module_path('empty')
+
+    with self.assertRaises(IOError):
+      module_resolver.resolve_module_path('/dev/null')
+
+  def testFileResolution(self):
+    module_resolver = FileModuleResolver(self.root_path)
+
+    project = Project(module_resolver=module_resolver)
+    self.assertEqual(len(project.module_list()), 0)
+    root_rule = project.resolve_rule('.:root_rule')
+    self.assertIsNotNone(root_rule)
+    self.assertEqual(len(project.module_list()), 1)
+
+  def testModuleNameMatching(self):
+    module_resolver = FileModuleResolver(self.root_path)
+
+    project = Project(module_resolver=module_resolver)
+    self.assertEqual(len(project.module_list()), 0)
+    rule_a = project.resolve_rule('a:rule_a')
+    self.assertIsNotNone(rule_a)
+    self.assertEqual(len(project.module_list()), 1)
+    self.assertIs(rule_a, project.resolve_rule('a/BUILD:rule_a'))
+    self.assertEqual(len(project.module_list()), 1)
+    self.assertIs(rule_a, project.resolve_rule('a/../a/BUILD:rule_a'))
+    self.assertEqual(len(project.module_list()), 1)
+    self.assertIs(rule_a, project.resolve_rule('b/../a/BUILD:rule_a'))
+    self.assertEqual(len(project.module_list()), 1)
+    self.assertIs(rule_a, project.resolve_rule('b/../a:rule_a'))
+    self.assertEqual(len(project.module_list()), 1)
+    self.assertIsNotNone(project.resolve_rule('b:rule_b'))
+    self.assertEqual(len(project.module_list()), 2)
+
+  def testValidModulePaths(self):
+    module_resolver = FileModuleResolver(self.root_path)
+
+    test_paths = [
+      ':root_rule',
+      '.:root_rule',
+      './:root_rule',
+      './BUILD:root_rule',
+      'a:rule_a',
+      'a/BUILD:rule_a',
+      'a/../a/BUILD:rule_a',
+      'b/../a/BUILD:rule_a',
+      'b/../a:rule_a',
+      'a/.:rule_a',
+      'a/./BUILD:rule_a',
+      'b:rule_b',
+      'b/:rule_b',
+      'b/BUILD:rule_b',
+      'b/c:rule_c',
+      'b/c/build_file.py:rule_c_file',
+    ]
+    for test_path in test_paths:
+      project = Project(module_resolver=module_resolver)
+      self.assertIsNotNone(project.resolve_rule(test_path))
+      self.assertEqual(len(project.module_list()), 1)
+
+  def testInvalidModulePaths(self):
+    module_resolver = FileModuleResolver(self.root_path)
+
+    invalid_test_paths = [
+      '.',
+      '/',
+    ]
+    for test_path in invalid_test_paths:
+      project = Project(module_resolver=module_resolver)
+      with self.assertRaises(NameError):
+        project.resolve_rule(test_path)
+      self.assertEqual(len(project.module_list()), 0)
+
+  def testMissingModules(self):
+    module_resolver = FileModuleResolver(self.root_path)
+
+    project = Project(module_resolver=module_resolver)
+    with self.assertRaises(OSError):
+      project.resolve_rule('x:rule_x')
+    self.assertEqual(len(project.module_list()), 0)
+
+    project = Project(module_resolver=module_resolver)
+    with self.assertRaises(OSError):
+      project.resolve_rule('/x:rule_x')
+    self.assertEqual(len(project.module_list()), 0)
+
+    project = Project(module_resolver=module_resolver)
+    with self.assertRaises(OSError):
+      project.resolve_rule('/BUILD:root_rule')
+    self.assertEqual(len(project.module_list()), 0)
+
+  def testMissingRules(self):
+    module_resolver = FileModuleResolver(self.root_path)
+
+    project = Project(module_resolver=module_resolver)
+    self.assertEqual(len(project.module_list()), 0)
+    self.assertIsNone(project.resolve_rule('.:x'))
+    self.assertEqual(len(project.module_list()), 1)
+    self.assertIsNone(project.resolve_rule('.:y'))
+    self.assertEqual(len(project.module_list()), 1)
+
+    project = Project(module_resolver=module_resolver)
+    self.assertEqual(len(project.module_list()), 0)
+    self.assertIsNone(project.resolve_rule('a:rule_x'))
+    self.assertEqual(len(project.module_list()), 1)
+    self.assertIsNone(project.resolve_rule('a/../a/BUILD:rule_x'))
+    self.assertEqual(len(project.module_list()), 1)
+    self.assertIsNone(project.resolve_rule('a/../a/BUILD:rule_y'))
+    self.assertEqual(len(project.module_list()), 1)
+
+
+if __name__ == '__main__':
+  unittest2.main()
diff --git a/anvil/rule.py b/anvil/rule.py
new file mode 100644
index 0000000..4195dc2
--- /dev/null
+++ b/anvil/rule.py
@@ -0,0 +1,329 @@
+# Copyright 2012 Google Inc. All Rights Reserved.
+
+"""A single rule metadata blob.
+Rules are defined by special rule functions (found under anvil.rules). They are
+meant to be immutable and reusable, and contain no state.
+"""
+
+__author__ = 'benvanik@google.com (Ben Vanik)'
+
+
+import base64
+import fnmatch
+import hashlib
+import imp
+import os
+import pickle
+import re
+import sys
+
+import util
+import version
+
+
+class Rule(object):
+  """A rule definition.
+  Rules are the base unit in a module and can depend on other rules via either
+  source (which depends on the outputs of the rule) or explicit dependencies
+  (which just requires that the other rule have been run before).
+
+  Sources can also refer to files, folders, or file globs. When a rule goes to
+  run a list of sources will be compiled from the outputs from the previous
+  rules as well as all real files on the file system.
+
+  Rules must define a _Context class that extends RuleContext. This context
+  will be used when executing the rule to store any temporary state and
+  execution progress. Rules should not be modified after their initial
+  construction, and instead the _Context should be used.
+  """
+
+  _whitespace_re = re.compile('\s', re.M)
+
+  def __init__(self, name, srcs=None, deps=None, src_filter=None,
+               *args, **kwargs):
+    """Initializes a rule.
+
+    Args:
+      name: A name for the rule - should be literal-like and contain no leading
+          or trailing whitespace.
+      srcs: A list of source strings or a single source string.
+      deps: A list of depdendency strings or a single dependency string.
+      src_filter: An inclusionary file name filter for all non-rule paths. If
+          defined only srcs that match this filter will be included.
+
+    Raises:
+      NameError: The given name is invalid (None/0-length).
+      TypeError: The type of an argument or value is invalid.
+    """
+    if not name or not len(name):
+      raise NameError('Invalid name')
+    if self._whitespace_re.search(name):
+      raise NameError('Name contains leading or trailing whitespace')
+    if name[0] == ':':
+      raise NameError('Name cannot start with :')
+    self.name = name
+
+    # Path will be updated when the parent module is set
+    self.parent_module = None
+    self.path = ':%s' % (name)
+
+    # All file/rule paths this rule depends on - as a set so no duplicates
+    self._dependent_paths = set([])
+
+    self.srcs = []
+    if isinstance(srcs, str):
+      if len(srcs):
+        self.srcs.append(srcs)
+    elif isinstance(srcs, list):
+      self.srcs.extend(srcs)
+    elif srcs != None:
+      raise TypeError('Invalid srcs type')
+    self._append_dependent_paths(self.srcs)
+
+    self.deps = []
+    if isinstance(deps, str):
+      if len(deps):
+        self.deps.append(deps)
+    elif isinstance(deps, list):
+      self.deps.extend(deps)
+    elif deps != None:
+      raise TypeError('Invalid deps type')
+    self._append_dependent_paths(self.deps, require_semicolon=True)
+
+    self.src_filter = None
+    if src_filter and len(src_filter):
+      self.src_filter = src_filter
+
+  def _append_dependent_paths(self, paths, require_semicolon=False):
+    """Appends a list of paths to the rule's dependent paths.
+    A dependent path is a file/rule that is required for execution and, if
+    changed, will invalidate cached versions of this rule.
+
+    Args:
+      paths: A list of paths to depend on.
+      require_semicolon: True if all of the given paths require a semicolon
+          (so they must be rules).
+
+    Raises:
+      NameError: One of the given paths is invalid.
+    """
+    util.validate_names(paths, require_semicolon=require_semicolon)
+    self._dependent_paths.update(paths)
+
+  def get_dependent_paths(self):
+    """Gets a list of all dependent paths.
+    Paths may be file paths or rule paths.
+
+    Returns:
+      A list of file/rule paths.
+    """
+    return self._dependent_paths.copy()
+
+  def set_parent_module(self, module):
+    """Sets the parent module of a rule.
+    This can only be called once.
+
+    Args:
+      module: New parent module for the rule.
+
+    Raises:
+      ValueError: The parent module has already been set.
+    """
+    if self.parent_module:
+      raise ValueError('Rule "%s" already has a parent module' % (self.name))
+    self.parent_module = module
+    self.path = '%s:%s' % (module.path, self.name)
+
+  def compute_cache_key(self):
+    """Calculates a unique key based on the rule type and its values.
+    This key may change when code changes, but is a fairly reliable way to
+    detect changes in rule values.
+
+    Returns:
+      A string that can be used to index this key in a dictionary. The string
+      may be very long.
+    """
+    # TODO(benvanik): faster serialization than pickle?
+    pickled_self = pickle.dumps(self)
+    pickled_str = base64.b64encode(pickled_self)
+    # Include framework version in the string to enable forced rebuilds on
+    # version change
+    unique_str = version.VERSION_STR + pickled_str
+    # Hash so that we return a reasonably-sized string
+    return hashlib.md5(unique_str).hexdigest()
+
+  def create_context(self, build_context):
+    """Creates a new RuleContext that is used to run the rule.
+    Rule implementations should return their own RuleContext type that
+    has custom behavior.
+
+    Args:
+      build_context: The current BuildContext that should be passed to the
+          RuleContext.
+
+    Returns:
+      A new RuleContext.
+    """
+    assert self._Context
+    return self._Context(build_context, self)
+
+
+# Active rule namespace that is capturing all new rule definitions
+# This should only be modified by RuleNamespace.discover
+_RULE_NAMESPACE = None
+
+class RuleNamespace(object):
+  """A namespace of rule type definitions and discovery services.
+  """
+
+  def __init__(self):
+    """Initializes a rule namespace."""
+    self.rule_types = {}
+
+  def populate_scope(self, scope):
+    """Populates the given scope dictionary with all of the rule types.
+
+    Args:
+      scope: Scope dictionary.
+    """
+    for rule_name in self.rule_types:
+      scope[rule_name] = self.rule_types[rule_name]
+
+  def add_rule_type(self, rule_name, rule_cls):
+    """Adds a rule type to the namespace.
+
+    Args:
+      rule_name: The name of the rule type exposed to modules.
+      rule_cls: Rule type class.
+    """
+    def rule_definition(name, *args, **kwargs):
+      rule = rule_cls(name, *args, **kwargs)
+      _emit_rule(rule)
+    rule_definition.rule_name = rule_name
+    if self.rule_types.has_key(rule_name):
+      raise KeyError('Rule type "%s" already defined' % (rule_name))
+    self.rule_types[rule_name] = rule_definition
+
+  def add_rule_type_fn(self, rule_type):
+    """Adds a rule type to the namespace.
+    This assumes the type is a function that is setup to emit the rule.
+    It should only be used by internal methods.
+
+    Args:
+      rule_type: Rule type.
+    """
+    rule_name = rule_type.rule_name
+    if self.rule_types.has_key(rule_name):
+      raise KeyError('Rule type "%s" already defined' % (rule_name))
+    self.rule_types[rule_name] = rule_type
+
+  def discover(self, path=None):
+    """Recursively searches the given path for rule type definitions.
+    Files are searched with the pattern '*_rules.py' for types decorated with
+    @build_rule.
+
+    Each module is imported as discovered into the python module list and will
+    be retained. Calling this multiple times with the same path has no effect.
+
+    Args:
+      path: Path to search for rule type modules. If omitted then the built-in
+          rule path will be searched instead. If the path points to a file it
+          will be checked, even if it does not match the name rules.
+    """
+    original_rule_types = self.rule_types.copy()
+    try:
+      if not path:
+        path = os.path.join(os.path.dirname(__file__), 'rules')
+      if os.path.isfile(path):
+        self._discover_in_file(path)
+      else:
+        for (dirpath, dirnames, filenames) in os.walk(path):
+          for filename in filenames:
+            if fnmatch.fnmatch(filename, '*_rules.py'):
+              self._discover_in_file(os.path.join(dirpath, filename))
+    except:
+      # Restore original types (don't take any of the discovered rules)
+      self.rule_types = original_rule_types
+      raise
+
+  def _discover_in_file(self, path):
+    """Loads the given python file to add all of its rules.
+
+    Args:
+      path: Python file path.
+    """
+    global _RULE_NAMESPACE
+    assert _RULE_NAMESPACE is None
+    _RULE_NAMESPACE = self
+    try:
+      name = os.path.splitext(os.path.basename(path))[0]
+      module = imp.load_source(name, path)
+    finally:
+      _RULE_NAMESPACE = None
+
+
+# Used by begin_capturing_emitted_rules/build_rule to track all emitted rules
+_EMIT_RULE_SCOPE = None
+
+def begin_capturing_emitted_rules():
+  """Begins capturing all rules emitted by @build_rule.
+  Use end_capturing_emitted_rules to end capturing and return the list of rules.
+  """
+  global _EMIT_RULE_SCOPE
+  assert not _EMIT_RULE_SCOPE
+  _EMIT_RULE_SCOPE = []
+
+def end_capturing_emitted_rules():
+  """Ends a rule capture and returns any rules emitted.
+
+  Returns:
+    A list of rules that were emitted by @build_rule.
+  """
+  global _EMIT_RULE_SCOPE
+  assert _EMIT_RULE_SCOPE is not None
+  rules = _EMIT_RULE_SCOPE
+  _EMIT_RULE_SCOPE = None
+  return rules
+
+def _emit_rule(rule):
+  """Emits a rule.
+  This should only ever be called while capturing.
+
+  Args:
+    rule: Rule that is being emitted.
+  """
+  global _EMIT_RULE_SCOPE
+  assert _EMIT_RULE_SCOPE is not None
+  _EMIT_RULE_SCOPE.append(rule)
+
+
+class build_rule(object):
+  """A decorator for build rule classes.
+  Use this to register build rule classes. A class decorated wtih this will be
+  exposed to modules with the given rule_name. It should be callable and, on
+  call, use emit_rule to emit a new rule.
+  """
+
+  def __init__(self, rule_name):
+    """Initializes the build rule decorator.
+
+    Args:
+      rule_name: The name of the rule type exposed to modules.
+    """
+    self.rule_name = rule_name
+
+  def __call__(self, cls):
+    # This wrapper function makes it possible to record all invocations of
+    # a rule while loading the module
+    def rule_definition(name, *args, **kwargs):
+      rule = cls(name, *args, **kwargs)
+      _emit_rule(rule)
+    rule_definition.rule_name = self.rule_name
+
+    # Add the (wrapped) rule type to the global namespace
+    # We support not having an active namespace so that tests can import
+    # rule files without dying
+    global _RULE_NAMESPACE
+    if _RULE_NAMESPACE:
+      _RULE_NAMESPACE.add_rule_type_fn(rule_definition)
+    return cls
diff --git a/anvil/rule_test.py b/anvil/rule_test.py
new file mode 100755
index 0000000..b90796a
--- /dev/null
+++ b/anvil/rule_test.py
@@ -0,0 +1,237 @@
+#!/usr/bin/python
+
+# Copyright 2012 Google Inc. All Rights Reserved.
+
+"""Tests for the rule module.
+"""
+
+__author__ = 'benvanik@google.com (Ben Vanik)'
+
+
+import os
+import unittest2
+
+from rule import *
+from test import FixtureTestCase
+
+
+class RuleTest(unittest2.TestCase):
+  """Behavioral tests of the Rule type."""
+
+  def testRuleNames(self):
+    with self.assertRaises(NameError):
+      Rule(None)
+    with self.assertRaises(NameError):
+      Rule('')
+    with self.assertRaises(NameError):
+      Rule(' ')
+    with self.assertRaises(NameError):
+      Rule(' a')
+    with self.assertRaises(NameError):
+      Rule('a ')
+    with self.assertRaises(NameError):
+      Rule(' a ')
+    with self.assertRaises(NameError):
+      Rule('a\n')
+    with self.assertRaises(NameError):
+      Rule('a\t')
+    with self.assertRaises(NameError):
+      Rule('a b')
+    with self.assertRaises(NameError):
+      Rule(':a')
+    rule = Rule('a')
+    self.assertEqual(rule.name, 'a')
+    self.assertEqual(rule.path, ':a')
+    Rule('\u0CA_\u0CA')
+
+  def testRuleSrcs(self):
+    rule = Rule('r')
+    self.assertEqual(len(rule.srcs), 0)
+
+    srcs = ['a', 'b', ':c']
+    rule = Rule('r', srcs=srcs)
+    self.assertEqual(len(rule.srcs), 3)
+    self.assertIsNot(rule.srcs, srcs)
+    srcs[0] = 'x'
+    self.assertEqual(rule.srcs[0], 'a')
+
+    srcs = 'a'
+    rule = Rule('r', srcs=srcs)
+    self.assertEqual(len(rule.srcs), 1)
+    self.assertEqual(rule.srcs[0], 'a')
+
+    rule = Rule('r', srcs=None)
+    rule = Rule('r', srcs='')
+    self.assertEqual(len(rule.srcs), 0)
+    with self.assertRaises(TypeError):
+      Rule('r', srcs={})
+    with self.assertRaises(TypeError):
+      Rule('r', srcs=[None])
+    with self.assertRaises(TypeError):
+      Rule('r', srcs=[''])
+    with self.assertRaises(TypeError):
+      Rule('r', srcs=[{}])
+    with self.assertRaises(NameError):
+      Rule('r', srcs=' a')
+    with self.assertRaises(NameError):
+      Rule('r', srcs='a ')
+    with self.assertRaises(NameError):
+      Rule('r', srcs=' a ')
+
+  def testRuleDeps(self):
+    rule = Rule('r')
+    self.assertEqual(len(rule.deps), 0)
+
+    deps = [':a', ':b', ':c']
+    rule = Rule('r', deps=deps)
+    self.assertEqual(len(rule.deps), 3)
+    self.assertIsNot(rule.deps, deps)
+    deps[0] = 'x'
+    self.assertEqual(rule.deps[0], ':a')
+
+    deps = ':a'
+    rule = Rule('r', deps=deps)
+    self.assertEqual(len(rule.deps), 1)
+    self.assertEqual(rule.deps[0], ':a')
+
+    rule = Rule('r', deps=None)
+    rule = Rule('r', deps='')
+    self.assertEqual(len(rule.deps), 0)
+    with self.assertRaises(TypeError):
+      Rule('r', deps={})
+    with self.assertRaises(TypeError):
+      Rule('r', deps=[None])
+    with self.assertRaises(TypeError):
+      Rule('r', deps=[''])
+    with self.assertRaises(TypeError):
+      Rule('r', deps={})
+    with self.assertRaises(NameError):
+      Rule('r', deps=' a')
+    with self.assertRaises(NameError):
+      Rule('r', deps='a ')
+    with self.assertRaises(NameError):
+      Rule('r', deps=' a ')
+
+  def testRuleDependentPaths(self):
+    rule = Rule('r')
+    self.assertEqual(rule.get_dependent_paths(), set([]))
+
+    rule = Rule('r', srcs=[':a', 'a.txt'])
+    self.assertEqual(rule.get_dependent_paths(), set([':a', 'a.txt']))
+
+    rule = Rule('r', deps=[':a', 'm:b'])
+    self.assertEqual(rule.get_dependent_paths(), set([':a', 'm:b']))
+
+    rule = Rule('r', srcs=['a.txt'], deps=[':b'])
+    self.assertEqual(rule.get_dependent_paths(), set(['a.txt', ':b']))
+
+    rule = Rule('r', srcs=[':b'], deps=[':b'])
+    self.assertEqual(rule.get_dependent_paths(), set([':b']))
+
+    with self.assertRaises(NameError):
+      Rule('r', deps=['a.txt'])
+
+    class RuleWithAttrs(Rule):
+      def __init__(self, name, extra_srcs=None, extra_deps=None,
+                   *args, **kwargs):
+        super(RuleWithAttrs, self).__init__(name, *args, **kwargs)
+        self.extra_srcs = extra_srcs[:]
+        self._append_dependent_paths(self.extra_srcs)
+        self.extra_deps = extra_deps[:]
+        self._append_dependent_paths(self.extra_deps, require_semicolon=True)
+
+    rule = RuleWithAttrs('r', srcs=['a.txt'], deps=[':b'],
+                         extra_srcs=['c.txt'], extra_deps=[':d'])
+    self.assertEqual(rule.get_dependent_paths(), set([
+        'a.txt', ':b', 'c.txt', ':d']))
+
+  def testRuleCacheKey(self):
+    rule1 = Rule('r1')
+    rule1_key = rule1.compute_cache_key()
+    self.assertIsNotNone(rule1_key)
+    self.assertGreater(len(rule1_key), 0)
+    self.assertEqual(rule1_key, rule1.compute_cache_key())
+    rule1.srcs.append('a')
+    self.assertNotEqual(rule1_key, rule1.compute_cache_key())
+
+    rule1 = Rule('r1')
+    rule2 = Rule('r1')
+    self.assertEqual(rule1.compute_cache_key(), rule2.compute_cache_key())
+    rule1 = Rule('r1')
+    rule2 = Rule('r2')
+    self.assertNotEqual(rule1.compute_cache_key(), rule2.compute_cache_key())
+
+    rule1 = Rule('r1', srcs='a')
+    rule2 = Rule('r1', srcs='a')
+    self.assertEqual(rule1.compute_cache_key(), rule2.compute_cache_key())
+    rule1 = Rule('r1', srcs='a')
+    rule2 = Rule('r1', srcs='b')
+    self.assertNotEqual(rule1.compute_cache_key(), rule2.compute_cache_key())
+    rule1 = Rule('r1', deps=':a')
+    rule2 = Rule('r1', deps=':a')
+    self.assertEqual(rule1.compute_cache_key(), rule2.compute_cache_key())
+    rule1 = Rule('r1', deps=':a')
+    rule2 = Rule('r1', deps=':b')
+    self.assertNotEqual(rule1.compute_cache_key(), rule2.compute_cache_key())
+    rule1 = Rule('r1', srcs='a', deps=':a')
+    rule2 = Rule('r1', srcs='a', deps=':a')
+    self.assertEqual(rule1.compute_cache_key(), rule2.compute_cache_key())
+    rule1 = Rule('r1', srcs='a', deps=':a')
+    rule2 = Rule('r1', srcs='b', deps=':b')
+    self.assertNotEqual(rule1.compute_cache_key(), rule2.compute_cache_key())
+
+  def testRuleFilter(self):
+    rule = Rule('a')
+    self.assertIsNone(rule.src_filter)
+    rule = Rule('a', src_filter='')
+    self.assertIsNone(rule.src_filter)
+    rule = Rule('a', src_filter='*.js')
+    self.assertEqual(rule.src_filter, '*.js')
+
+
+class RuleNamespaceTest(FixtureTestCase):
+  """Behavioral tests of the Rule type."""
+  fixture = 'rules'
+
+  def testManual(self):
+    ns = RuleNamespace()
+    self.assertEqual(len(ns.rule_types), 0)
+
+    class MockRule1(Rule):
+      pass
+    ns.add_rule_type('mock_rule_1', MockRule1)
+    self.assertEqual(len(ns.rule_types), 1)
+
+    with self.assertRaises(KeyError):
+      ns.add_rule_type('mock_rule_1', MockRule1)
+
+  def testDiscovery(self):
+    ns = RuleNamespace()
+    ns.discover()
+    self.assertTrue(ns.rule_types.has_key('file_set'))
+
+    rule_path = self.root_path
+    ns = RuleNamespace()
+    ns.discover(rule_path)
+    self.assertEqual(len(ns.rule_types), 3)
+    self.assertFalse(ns.rule_types.has_key('file_set'))
+    self.assertTrue(ns.rule_types.has_key('rule_a'))
+    self.assertTrue(ns.rule_types.has_key('rule_b'))
+    self.assertTrue(ns.rule_types.has_key('rule_c'))
+    self.assertFalse(ns.rule_types.has_key('rule_x'))
+
+    rule_path = os.path.join(self.root_path, 'dupe.py')
+    ns = RuleNamespace()
+    with self.assertRaises(KeyError):
+      ns.discover(rule_path)
+    self.assertEqual(len(ns.rule_types), 0)
+
+    rule_path = os.path.join(self.root_path, 'more', 'more_rules.py')
+    ns = RuleNamespace()
+    ns.discover(rule_path)
+    self.assertEqual(len(ns.rule_types), 1)
+    self.assertTrue(ns.rule_types.has_key('rule_c'))
+
+
+if __name__ == '__main__':
+  unittest2.main()
diff --git a/anvil/rules/TODO b/anvil/rules/TODO
new file mode 100644
index 0000000..f3c3671
--- /dev/null
+++ b/anvil/rules/TODO
@@ -0,0 +1,202 @@
+Some ideas for rules, based on old code:
+
+# ==============================================================================
+# Common Tasks
+# ==============================================================================
+
+CopyFilesTask
+ExecutableTask
+- JavaExecutableTask
+- NodeExecutableTask
+- PythonExecutableTask
+
+# ==============================================================================
+# Core
+# ==============================================================================
+
+copy_files(
+    name='a',
+    srcs=['a/file.txt'])
+- results in out/a/file.txt
+
+copy_files(
+    name='a',
+    srcs=glob('**/*.txt'))
+- results in out/things/a/file.txt + others
+
+concat_files(
+    name='catted',
+    srcs=['a.txt'] + glob('**/*.txt'))
+- results in out/catted
+
+concat_files(
+    name='catted',
+    srcs=['a.txt'] + glob('**/*.txt'),
+    out='catted.txt')
+- results in out/catted.txt
+
+template_files(
+    name='templated_txt',
+    srcs=glob('**/*.txt'),
+    params={
+        'author': 'bob',
+        'year': '2012',
+        })
+- results in out/...txt with ${author} and ${year} replaced
+
+# ==============================================================================
+# Audio
+# ==============================================================================
+
+compile_soundbank(
+    name='bank1',
+    srcs=['*.wav'],
+    out='assets/audio/')
+- creates out/assets/audio/bank1.wav + bank1.json
+
+SOUNDBANK_FORMATS = select_any({
+    'RELEASE': ['audio/wav', 'audio/mpeg', 'audio/ogg', 'audio/mp4',],
+    }, ['audio/wav',])
+transcode_audio(
+    name='encoded_banks',
+    srcs=[':bank1', ':bank2'],
+    formats=SOUNDBANK_FORMATS)
+- encodes all input audio files to the specified formats, updating the json
+  with any new data sources - in this case, it files bank1.json and bank2.json,
+  transcodes all sources for them, and updates their respective json files -
+  the output files are all inputs + the transcoded files
+
+generate_soundbank_js(
+    name='bank_js',
+    srcs=':encoded_banks',
+    namespace='foo.audio',
+    gen='foo/audio/')
+- for each json file generates a js file from the json metadata, resulting in
+  gen/foo/audio/bank1.js (class foo.audio.bank1) + bank2.js
+
+compile_tracklist(
+    name='music',
+    srcs=['*.ogg'],)
+- creates out/assets/audio/music.ogg (copy) + music.json
+
+TRACKLIST_FORMATS=select_any({
+    'RELEASE': ['audio/mpeg', 'audio/ogg', 'audio/mp4',],
+    }, ['audio/ogg',])
+transcode_audio(
+    name='encoded_music',
+    srcs=':music',
+    formats=TRACKLIST_FORMATS)
+generate_tracklist_js(
+    name='music_js',
+    srcs=':encoded_music',
+    namespace='foo.audio',
+    gen='foo/audio/')
+- for each json file generates a js file from the json metadata, resulting in
+  gen/foo/audio/music.js (class foo.audio.music)
+
+
+# ==============================================================================
+# GLSL
+# ==============================================================================
+
+compile_glsl(
+    name='compiled_glsl',
+    srcs=glob('assets/glsl/**/*.glsl*'))
+- compiles all .glsl files into .json files, such as assets/glsl/a.glsl ->
+  out/assets/glsl/a.json - any glsllib files are ignored, but may be used by
+  the compiler
+  outputs are only the json files
+
+generate_glsl_js(
+    name='glsl_js',
+    srcs=':compiled_glsl',
+    namespace='foo.glsl',
+    gen='foo/glsl/')
+- for each json file generates a js file from the json metadata, resulting in
+  gen/foo/glsl/a.js (class foo.glsl.a)
+
+
+# ==============================================================================
+# CSS
+# ==============================================================================
+
+compile_gss(
+    name='page_gss',
+    srcs=glob('assets/css/**/*.gss'),
+    out='css/page_gss.css',
+    gen='css/page_gss.js')
+- compiles all gss into out/css/page.css, and drops the map file to
+  gen/css/page.js
+
+
+# ==============================================================================
+# Closure JS
+# ==============================================================================
+
+JS_NAMESPACES=['myns1', 'myns2']
+
+fix_closure_js(
+    name='fix_js',
+    srcs=glob('src/**/*.js'),
+    namespaces=JS_NAMESPACES)
+- runs fixjsstyle on all sources (with the same args as lint_closure_js) and
+  returns all srcs as outputs
+
+lint_closure_js(
+    name='lint_js',
+    srcs=':fix_js',
+    namespaces=JS_NAMESPACES)
+- runs gjslist over all of the source files with the following args:
+  --multiprocess
+  --strict
+  --jslint_error=all
+  --closurized_namespaces=goog,gf, + namespaces
+  and returns all srcs as outputs
+
+file_set(
+    name='all_js',
+    src_filter='*.js',
+    srcs=[':fix_js', ':audio_rules', ':page_gss',])
+generate_closure_deps_js(
+    name='deps_js',
+    srcs=[':all_js'],
+    gen='my_deps.js')
+- runs genjsdeps on all sources and generate the gen/my_deps.js file
+  note that this pulls in all generated JS code by sourcing from all rules
+
+file_set(
+    name='uncompiled',
+    deps=[':deps_js'])
+- a synthetic rule to allow for easy 'uncompiled' building
+
+SHARED_JS_FLAGS=['--define=foo=false']
+compile_closure_js(
+    name='compiled_js',
+    srcs=[':all_js', ':deps_js',],
+    out='js/compiled.js',
+    root_namespace='myns1.start',
+    compiler_flags=SHARED_JS_FLAGS + select_many({
+        'RELEASE': ['--define=gf.BUILD_CLIENT=false',
+                    '--define=goog.DEBUG=false',
+                    '--define=goog.asserts.ENABLE_ASSERTS=false',],
+        })
+- creates a out/js/compiled.js file based on all sources
+  could add source_map='foo.map' to enable source mapping output
+  wrap_with_global='s' to do (function(){...})(s)
+
+
+# ==============================================================================
+# Future...
+# ==============================================================================
+
+* wget/curl-esque rules w/ caching (grab text/json/manifest from somewhere)
+* SASS/LESS/etc
+* uglifyjs/etc
+* jslint
+* html/json/etc linting
+* localization utils (common format translations)
+* soy compiler
+* images/texture compression
+* spriting
+* more advanced templating with mako
+* git info (get current commit hash/etc) - embedded version #s
diff --git a/anvil/rules/__init__.py b/anvil/rules/__init__.py
new file mode 100644
index 0000000..7b692e2
--- /dev/null
+++ b/anvil/rules/__init__.py
@@ -0,0 +1,6 @@
+# Copyright 2012 Google Inc. All Rights Reserved.
+
+"""
+"""
+
+__author__ = 'benvanik@google.com (Ben Vanik)'
diff --git a/anvil/rules/core_rules.py b/anvil/rules/core_rules.py
new file mode 100644
index 0000000..e4cd83b
--- /dev/null
+++ b/anvil/rules/core_rules.py
@@ -0,0 +1,243 @@
+# Copyright 2012 Google Inc. All Rights Reserved.
+
+"""Core rules for the build system.
+"""
+
+__author__ = 'benvanik@google.com (Ben Vanik)'
+
+
+import io
+import os
+import shutil
+import string
+
+from anvil.context import RuleContext
+from anvil.rule import Rule, build_rule
+from anvil.task import Task
+
+
+@build_rule('file_set')
+class FileSetRule(Rule):
+  """A file set aggregation rule.
+  All source files are globbed together and de-duplicated before being passed
+  on as outputs. If a src_filter is provided then it is used to filter all
+  sources.
+
+  File set rules can be used as synthetic rules for making dependencies easier
+  to manage, or for filtering many rules into one.
+
+  Inputs:
+    srcs: Source file paths.
+
+  Outputs:
+    All of the source file paths, passed-through unmodified.
+  """
+
+  def __init__(self, name, *args, **kwargs):
+    """Initializes a file set rule.
+
+    Args:
+      name: Rule name.
+    """
+    super(FileSetRule, self).__init__(name, *args, **kwargs)
+
+  class _Context(RuleContext):
+    def begin(self):
+      super(FileSetRule._Context, self).begin()
+      self._append_output_paths(self.src_paths)
+      self._succeed()
+
+
+@build_rule('copy_files')
+class CopyFilesRule(Rule):
+  """Copy files from one path to another.
+  Copies all source files to the output path.
+
+  The resulting structure will match that of all files relative to the path of
+  the module the rule is in. For example, srcs='a.txt' will result in
+  '$out/a.txt', and srcs='dir/a.txt' will result in '$out/dir/a.txt'.
+
+  If a src_filter is provided then it is used to filter all sources.
+
+  This copies all files and preserves all file metadata, but does not preserve
+  directory metadata.
+
+  Inputs:
+    srcs: Source file paths.
+
+  Outputs:
+    All of the copied files in the output path.
+  """
+
+  def __init__(self, name, *args, **kwargs):
+    """Initializes a copy files rule.
+
+    Args:
+      name: Rule name.
+    """
+    super(CopyFilesRule, self).__init__(name, *args, **kwargs)
+
+  class _Context(RuleContext):
+    def begin(self):
+      super(CopyFilesRule._Context, self).begin()
+
+      # Get all source -> output paths (and ensure directories exist)
+      file_pairs = []
+      for src_path in self.src_paths:
+        out_path = self._get_out_path_for_src(src_path)
+        self._ensure_output_exists(os.path.dirname(out_path))
+        self._append_output_paths([out_path])
+        file_pairs.append((src_path, out_path))
+
+      # Async issue copying task
+      d = self._run_task_async(_CopyFilesTask(
+          self.build_env, file_pairs))
+      self._chain(d)
+
+
+class _CopyFilesTask(Task):
+  def __init__(self, build_env, file_pairs, *args, **kwargs):
+    super(_CopyFilesTask, self).__init__(build_env, *args, **kwargs)
+    self.file_pairs = file_pairs
+
+  def execute(self):
+    for file_pair in self.file_pairs:
+      shutil.copy2(file_pair[0], file_pair[1])
+    return True
+
+
+@build_rule('concat_files')
+class ConcatFilesRule(Rule):
+  """Concatenate many files into one.
+  Takes all source files and concatenates them together. The order is based on
+  the ordering of the srcs list, and all files are treated as binary.
+
+  Note that if referencing other rules or globs the order of files may be
+  undefined, so if order matters try to enumerate files manually.
+
+  TODO(benvanik): support a text mode?
+
+  Inputs:
+    srcs: Source file paths. The order is the order in which they will be
+        concatenated.
+    out: Optional output name. If none is provided than the rule name will be
+        used.
+
+  Outputs:
+    All of the srcs concatenated into a single file path. If no out is specified
+    a file with the name of the rule will be created.
+  """
+
+  def __init__(self, name, out=None, *args, **kwargs):
+    """Initializes a concatenate files rule.
+
+    Args:
+      name: Rule name.
+      out: Optional output name.
+    """
+    super(ConcatFilesRule, self).__init__(name, *args, **kwargs)
+    self.out = out
+
+  class _Context(RuleContext):
+    def begin(self):
+      super(ConcatFilesRule._Context, self).begin()
+
+      output_path = self._get_out_path(name=self.rule.out)
+      self._ensure_output_exists(os.path.dirname(output_path))
+      self._append_output_paths([output_path])
+
+      # Async issue concat task
+      d = self._run_task_async(_ConcatFilesTask(
+          self.build_env, self.src_paths, output_path))
+      self._chain(d)
+
+
+class _ConcatFilesTask(Task):
+  def __init__(self, build_env, src_paths, output_path, *args, **kwargs):
+    super(_ConcatFilesTask, self).__init__(build_env, *args, **kwargs)
+    self.src_paths = src_paths
+    self.output_path = output_path
+
+  def execute(self):
+    with io.open(self.output_path, 'wt') as out_file:
+      for src_path in self.src_paths:
+        with io.open(src_path, 'rt') as in_file:
+          out_file.write(in_file.read())
+    return True
+
+
+@build_rule('template_files')
+class TemplateFilesRule(Rule):
+  """Applies simple templating to a set of files.
+  Processes each source file replacing a list of strings with corresponding
+  strings.
+
+  This uses the Python string templating functionality documented here:
+  http://docs.python.org/library/string.html#template-strings
+
+  Identifiers in the source template should be of the form "${identifier}", each
+  of which maps to a key in the params dictionary.
+
+  In order to prevent conflicts, it is strongly encouraged that a new_extension
+  value is provided. If a source file has an extension it will be replaced with
+  the specified one, and files without extensions will have it added.
+
+  TODO(benvanik): more advanced template vars? perhaps regex?
+
+  Inputs:
+    srcs: Source file paths.
+    new_extension: The extension to replace (or add) to all output files, with a
+        leading dot ('.txt').
+    params: A dictionary of key-value replacement parameters.
+
+  Outputs:
+    One file for each source file with the templating rules applied.
+  """
+
+  def __init__(self, name, new_extension=None, params=None, *args, **kwargs):
+    """Initializes a file templating rule.
+
+    Args:
+      name: Rule name.
+      new_extension: Replacement extension ('.txt').
+      params: A dictionary of key-value replacement parameters.
+    """
+    super(TemplateFilesRule, self).__init__(name, *args, **kwargs)
+    self.new_extension = new_extension
+    self.params = params
+
+  class _Context(RuleContext):
+    def begin(self):
+      super(TemplateFilesRule._Context, self).begin()
+
+      # Get all source -> output paths (and ensure directories exist)
+      file_pairs = []
+      for src_path in self.src_paths:
+        out_path = self._get_out_path_for_src(src_path)
+        if self.rule.new_extension:
+          out_path = os.path.splitext(out_path)[0] + self.rule.new_extension
+        self._ensure_output_exists(os.path.dirname(out_path))
+        self._append_output_paths([out_path])
+        file_pairs.append((src_path, out_path))
+
+      # Async issue templating task
+      d = self._run_task_async(_TemplateFilesTask(
+          self.build_env, file_pairs, self.rule.params))
+      self._chain(d)
+
+
+class _TemplateFilesTask(Task):
+  def __init__(self, build_env, file_pairs, params, *args, **kwargs):
+    super(_TemplateFilesTask, self).__init__(build_env, *args, **kwargs)
+    self.file_pairs = file_pairs
+    self.params = params
+
+  def execute(self):
+    for file_pair in self.file_pairs:
+      with io.open(file_pair[0], 'rt') as f:
+        template_str = f.read()
+      template = string.Template(template_str)
+      result_str = template.substitute(self.params)
+      with io.open(file_pair[1], 'wt') as f:
+        f.write(result_str)
+    return True
diff --git a/anvil/rules/core_rules_test.py b/anvil/rules/core_rules_test.py
new file mode 100755
index 0000000..54d5d27
--- /dev/null
+++ b/anvil/rules/core_rules_test.py
@@ -0,0 +1,210 @@
+#!/usr/bin/python
+
+# Copyright 2012 Google Inc. All Rights Reserved.
+
+"""Tests for the core_rules module.
+"""
+
+__author__ = 'benvanik@google.com (Ben Vanik)'
+
+
+import os
+import unittest2
+
+from anvil.context import BuildContext, BuildEnvironment, Status
+from anvil.project import FileModuleResolver, Project
+from anvil.test import FixtureTestCase
+from core_rules import *
+
+
+class RuleTestCase(FixtureTestCase):
+  def assertRuleResultsEqual(self, build_ctx, rule_path, expected_file_matches,
+      output_prefix=''):
+    results = build_ctx.get_rule_results(rule_path)
+    self.assertEqual(results[0], Status.SUCCEEDED)
+    output_paths = results[1]
+
+    root_path = os.path.join(build_ctx.build_env.root_path, output_prefix)
+    result_file_list = [os.path.relpath(f, root_path) for f in output_paths]
+    self.assertEqual(
+        set(result_file_list),
+        set(expected_file_matches))
+
+
+class FileSetRuleTest(RuleTestCase):
+  """Behavioral tests of the FileSetRule type."""
+  fixture='core_rules/file_set'
+
+  def setUp(self):
+    super(FileSetRuleTest, self).setUp()
+    self.build_env = BuildEnvironment(root_path=self.root_path)
+
+  def test(self):
+    project = Project(module_resolver=FileModuleResolver(self.root_path))
+
+    with BuildContext(self.build_env, project) as ctx:
+      self.assertTrue(ctx.execute_sync([
+          ':a',
+          ':a_glob',
+          ':b_ref',
+          ':all_glob',
+          ':combo',
+          ':dupes',
+          'dir:b',
+          'dir:b_glob',
+          ]))
+
+      self.assertRuleResultsEqual(ctx,
+          ':a', ['a.txt',])
+      self.assertRuleResultsEqual(ctx,
+          ':a_glob', ['a.txt',])
+      self.assertRuleResultsEqual(ctx,
+          ':b_ref', ['dir/b.txt',])
+      self.assertRuleResultsEqual(ctx,
+          ':all_glob', ['a.txt', 'dir/b.txt',])
+      self.assertRuleResultsEqual(ctx,
+          ':combo', ['a.txt', 'dir/b.txt',])
+      self.assertRuleResultsEqual(ctx,
+          ':dupes', ['a.txt', 'dir/b.txt',])
+      self.assertRuleResultsEqual(ctx,
+          'dir:b', ['dir/b.txt',])
+      self.assertRuleResultsEqual(ctx,
+          'dir:b_glob', ['dir/b.txt',])
+
+
+class CopyFilesRuleTest(RuleTestCase):
+  """Behavioral tests of the CopyFilesRule type."""
+  fixture='core_rules/copy_files'
+
+  def setUp(self):
+    super(CopyFilesRuleTest, self).setUp()
+    self.build_env = BuildEnvironment(root_path=self.root_path)
+
+  def test(self):
+    project = Project(module_resolver=FileModuleResolver(self.root_path))
+
+    with BuildContext(self.build_env, project) as ctx:
+      self.assertTrue(ctx.execute_sync([
+          ':copy_all_txt',
+          'dir:copy_c',
+          ]))
+
+      self.assertRuleResultsEqual(ctx,
+          ':copy_all_txt', ['a.txt',
+                            'dir/b.txt'],
+          output_prefix='build-out')
+      self.assertFileContents(
+          os.path.join(self.root_path, 'build-out/a.txt'),
+          'a\n')
+      self.assertFileContents(
+          os.path.join(self.root_path, 'build-out/dir/b.txt'),
+          'b\n')
+
+      self.assertRuleResultsEqual(ctx,
+          'dir:copy_c', ['dir/c.not-txt',],
+          output_prefix='build-out')
+      self.assertFileContents(
+          os.path.join(self.root_path, 'build-out/dir/c.not-txt'),
+          'c\n')
+
+
+class ConcatFilesRuleTest(RuleTestCase):
+  """Behavioral tests of the ConcatFilesRule type."""
+  fixture='core_rules/concat_files'
+
+  def setUp(self):
+    super(ConcatFilesRuleTest, self).setUp()
+    self.build_env = BuildEnvironment(root_path=self.root_path)
+
+  def test(self):
+    project = Project(module_resolver=FileModuleResolver(self.root_path))
+
+    with BuildContext(self.build_env, project) as ctx:
+      self.assertTrue(ctx.execute_sync([
+          ':concat',
+          ':concat_out',
+          ':concat_template',
+          ':templated',
+          ]))
+
+      self.assertRuleResultsEqual(ctx,
+          ':concat', ['concat',],
+          output_prefix='build-out')
+      self.assertFileContents(
+          os.path.join(self.root_path, 'build-out/concat'),
+          '1\n2\n3\n4\n')
+
+      self.assertRuleResultsEqual(ctx,
+          ':concat_out', ['concat.txt',],
+          output_prefix='build-out')
+      self.assertFileContents(
+          os.path.join(self.root_path, 'build-out/concat.txt'),
+          '1\n2\n3\n4\n')
+
+      self.assertRuleResultsEqual(ctx,
+          ':concat_template', ['concat_template',],
+          output_prefix='build-out')
+      self.assertFileContents(
+          os.path.join(self.root_path, 'build-out/concat_template'),
+          '1\n2\n3\n4\nx${hello}x\n1\n2\n3\n4\n')
+      self.assertRuleResultsEqual(ctx,
+          ':templated', ['concat_template.out',],
+          output_prefix='build-out')
+      self.assertFileContents(
+          os.path.join(self.root_path, 'build-out/concat_template.out'),
+          '1\n2\n3\n4\nxworld!x\n1\n2\n3\n4\n')
+
+
+class TemplateFilesRuleTest(RuleTestCase):
+  """Behavioral tests of the TemplateFilesRule type."""
+  fixture='core_rules/template_files'
+
+  def setUp(self):
+    super(TemplateFilesRuleTest, self).setUp()
+    self.build_env = BuildEnvironment(root_path=self.root_path)
+
+  def test(self):
+    project = Project(module_resolver=FileModuleResolver(self.root_path))
+
+    with BuildContext(self.build_env, project) as ctx:
+      self.assertTrue(ctx.execute_sync([
+          ':template_all',
+          ':template_dep_2',
+          ]))
+
+      self.assertRuleResultsEqual(ctx,
+          ':template_all', ['a.txt',
+                            'dir/b.txt'],
+          output_prefix='build-out')
+      self.assertFileContents(
+          os.path.join(self.root_path, 'build-out/a.txt'),
+          '123world456\n')
+      self.assertFileContents(
+          os.path.join(self.root_path, 'build-out/dir/b.txt'),
+          'b123world456\n')
+
+      self.assertRuleResultsEqual(ctx,
+          ':template_dep_1', ['a.nfo',
+                              'dir/b.nfo'],
+          output_prefix='build-out')
+      self.assertFileContents(
+          os.path.join(self.root_path, 'build-out/a.nfo'),
+          '123${arg2}456\n')
+      self.assertFileContents(
+          os.path.join(self.root_path, 'build-out/dir/b.nfo'),
+          'b123${arg2}456\n')
+
+      self.assertRuleResultsEqual(ctx,
+          ':template_dep_2', ['a.out',
+                              'dir/b.out'],
+          output_prefix='build-out')
+      self.assertFileContents(
+          os.path.join(self.root_path, 'build-out/a.out'),
+          '123world!456\n')
+      self.assertFileContents(
+          os.path.join(self.root_path, 'build-out/dir/b.out'),
+          'b123world!456\n')
+
+
+if __name__ == '__main__':
+  unittest2.main()
diff --git a/anvil/task.py b/anvil/task.py
new file mode 100644
index 0000000..9801a23
--- /dev/null
+++ b/anvil/task.py
@@ -0,0 +1,351 @@
+# Copyright 2012 Google Inc. All Rights Reserved.
+
+"""Task/multiprocessing support.
+"""
+
+__author__ = 'benvanik@google.com (Ben Vanik)'
+
+
+import multiprocessing
+import os
+import re
+import subprocess
+import sys
+import time
+
+from async import Deferred
+
+
+class Task(object):
+  """Abstract base type for small tasks.
+  A task should be the smallest possible unit of work a Rule may want to
+  perform. Examples include copying a set of files, converting an mp3, or
+  compiling some code.
+
+  Tasks can execute in parallel with other tasks, and are run in a seperate
+  process. They must be pickleable and should access no global state.
+
+  TODO(benvanik): add support for logging - a Queue that pushes back
+      log/progress messages?
+  """
+
+  def __init__(self, build_env, *args, **kwargs):
+    """Initializes a task.
+
+    Args:
+      build_env: The build environment for state.
+    """
+    self.build_env = build_env
+
+  def execute(self):
+    """Executes the task.
+    This method will be called in a separate process and should not use any
+    state not accessible from the Task. The Task will have been pickled and
+    will not be merged back with the parent.
+
+    The result of this method must be pickleable and will be sent back to the
+    deferred callback. If an exception is raised it will be wrapped in the
+    deferred's errback.
+
+    Returns:
+      A result to pass back to the deferred callback.
+    """
+    raise NotImplementedError()
+
+
+class ExecutableError(Exception):
+  """An exception concerning the execution of a command.
+  """
+
+  def __init__(self, return_code, *args, **kwargs):
+    """Initializes an executable error.
+
+    Args:
+      return_code: The return code of the application.
+    """
+    super(ExecutableError, self).__init__(*args, **kwargs)
+    self.return_code = return_code
+
+  def __str__(self):
+    return 'ExecutableError: call returned %s' % (self.return_code)
+
+
+class ExecutableTask(Task):
+  """A task that executes a command in the shell.
+
+  If the call returns an error an ExecutableError is raised.
+  """
+
+  def __init__(self, build_env, executable_name, call_args=None,
+               *args, **kwargs):
+    """Initializes an executable task.
+
+    Args:
+      build_env: The build environment for state.
+      executable_name: The name (or full path) of an executable.
+      call_args: Arguments to pass to the executable.
+    """
+    super(ExecutableTask, self).__init__(build_env, *args, **kwargs)
+    self.executable_name = executable_name
+    self.call_args = call_args if call_args else []
+
+  def execute(self):
+    p = subprocess.Popen([self.executable_name] + self.call_args,
+                         bufsize=-1, # system default
+                         stdout=subprocess.PIPE,
+                         stderr=subprocess.PIPE)
+
+    # TODO(benvanik): would be nice to support a few modes here - enabling
+    #     streaming output from the process (for watching progress/etc).
+    #     This right now just waits until it exits and grabs everything.
+    (stdoutdata, stderrdata) = p.communicate()
+
+    return_code = p.returncode
+    if return_code != 0:
+      raise ExecutableError(return_code=return_code)
+
+    return (stdoutdata, stderrdata)
+
+
+class JavaExecutableTask(ExecutableTask):
+  """A task that executes a Java class in the shell.
+  """
+
+  def __init__(self, build_env, jar_path, call_args=None, *args, **kwargs):
+    """Initializes an executable task.
+
+    Args:
+      build_env: The build environment for state.
+      jar_path: The name (or full path) of a jar to execute.
+      call_args: Arguments to pass to the executable.
+    """
+    executable_name = 'java'
+    call_args = ['-jar', jar_path] + call_args if call_args else []
+    super(JavaExecutableTask, self).__init__(build_env, executable_name,
+        call_args, *args, **kwargs)
+
+  @classmethod
+  def detect_java_version(cls, java_executable='java'):
+    """Gets the version number of Java.
+
+    Returns:
+      The version in the form of '1.7.0', or None if Java is not found.
+    """
+    try:
+      p = subprocess.Popen([java_executable, '-version'],
+                           stderr=subprocess.PIPE)
+      line = p.communicate()[1]
+      return re.search(r'[0-9\.]+', line).group()
+    except:
+      return None
+
+
+# TODO(benvanik): node.js-specific executable task
+# class NodeExecutableTask(ExecutableTask):
+#   pass
+
+
+# TODO(benvanik): python-specific executable task
+# class PythonExecutableTask(ExecutableTask):
+#   pass
+
+
+class TaskExecutor(object):
+  """An abstract queue for task execution.
+  """
+
+  def __init__(self, *args, **kwargs):
+    """Initializes a task executor.
+    """
+    self.closed = False
+    self._running_count = 0
+
+  def __enter__(self):
+    return self
+
+  def __exit__(self, type, value, traceback):
+    if not self.closed:
+      self.close()
+
+  def has_any_running(self):
+    """
+    Returns:
+      True if there are any tasks still running.
+    """
+    return self._running_count > 0
+
+  def run_task_async(self, task):
+    """Queues a new task for execution.
+
+    Args:
+      task: Task object to execute on a worker thread.
+
+    Returns:
+      A deferred that signals completion of the task. The results of the task
+      will be passed to the callback.
+
+    Raises:
+      RuntimeError: Invalid executor state.
+    """
+    raise NotImplementedError()
+
+  def wait(self, deferreds):
+    """Blocks waiting on a list of deferreds until they all complete.
+    This should laregly be used for testing. The deferreds must have been
+    returned from run_task_async.
+
+    Args:
+      deferreds: A list of Deferreds (or one).
+    """
+    raise NotImplementedError()
+
+
+  def close(self, graceful=True):
+    """Closes the executor, waits for all tasks to complete, and joins.
+    This will block until tasks complete.
+
+    Args:
+      graceful: True to allow outstanding tasks to complete.
+
+    Raises:
+      RuntimeError: Invalid executor state.
+    """
+    raise NotImplementedError()
+
+
+class InProcessTaskExecutor(TaskExecutor):
+  """A simple inline task executor.
+  Blocks on task execution, performing all tasks in the running process.
+  This makes testing simpler as all deferreds are complete upon callback.
+  """
+
+  def __init__(self, *args, **kwargs):
+    """Initializes a task executor.
+    """
+    super(InProcessTaskExecutor, self).__init__(*args, **kwargs)
+
+  def run_task_async(self, task):
+    if self.closed:
+      raise RuntimeError('Executor has been closed and cannot run new tasks')
+
+    deferred = Deferred()
+    try:
+      result = task.execute()
+      deferred.callback(result)
+    except Exception as e:
+      deferred.errback(exception=e)
+    return deferred
+
+  def wait(self, deferreds):
+    pass
+
+  def close(self, graceful=True):
+    if self.closed:
+      raise RuntimeError(
+          'Attempting to close an executor that has already been closed')
+    self.closed = True
+    self._running_count = 0
+
+
+class MultiProcessTaskExecutor(TaskExecutor):
+  """A pool for multiprocess task execution.
+  """
+
+  def __init__(self, worker_count=None, *args, **kwargs):
+    """Initializes a task executor.
+    This may take a bit to run, as the process pool is primed.
+
+    Args:
+      worker_count: Number of worker threads to use when building. None to use
+          as many processors as are available.
+    """
+    super(MultiProcessTaskExecutor, self).__init__(*args, **kwargs)
+    self.worker_count = worker_count
+    try:
+      self._pool = multiprocessing.Pool(processes=self.worker_count,
+                                        initializer=_task_initializer)
+    except OSError as e: # pragma: no cover
+      print e
+      print 'Unable to initialize multiprocessing!'
+      if sys.platform == 'cygwin':
+        print ('Cygwin has known issues with multiprocessing and there\'s no '
+               'workaround. Boo!')
+      print 'Try running with -j 1 to disable multiprocessing'
+      raise
+    self._waiting_deferreds = {}
+
+  def run_task_async(self, task):
+    if self.closed:
+      raise RuntimeError('Executor has been closed and cannot run new tasks')
+
+    # Pass on results to the defered
+    deferred = Deferred()
+    def _thunk_callback(*args, **kwargs):
+      self._running_count = self._running_count - 1
+      del self._waiting_deferreds[deferred]
+      if len(args) and isinstance(args[0], Exception):
+        deferred.errback(exception=args[0])
+      else:
+        deferred.callback(*args)
+
+    # Queue
+    self._running_count = self._running_count + 1
+    async_result = self._pool.apply_async(_task_thunk, [task],
+        callback=_thunk_callback)
+    self._waiting_deferreds[deferred] = async_result
+
+    return deferred
+
+  def wait(self, deferreds):
+    try:
+      iter(deferreds)
+    except:
+      deferreds = [deferreds]
+    spin_deferreds = []
+    for deferred in deferreds:
+      if deferred.is_done():
+        continue
+      if not self._waiting_deferreds.has_key(deferred):
+        # Not a deferred created by this - queue for a spin wait
+        spin_deferreds.append(deferred)
+      else:
+        async_result = self._waiting_deferreds[deferred]
+        async_result.wait()
+    for deferred in spin_deferreds:
+      while not deferred.is_done():
+        time.sleep(0.01)
+
+  def close(self, graceful=True):
+    if self.closed:
+      raise RuntimeError(
+          'Attempting to close an executor that has already been closed')
+    self.closed = True
+    if graceful:
+      self._pool.close()
+    else:
+      self._pool.terminate()
+    self._pool.join()
+    self._running_count = 0
+    self._waiting_deferreds.clear()
+
+def _task_initializer(): # pragma: no cover
+  """Task executor process initializer, used by MultiProcessTaskExecutor.
+  Called once on each process the TaskExecutor uses.
+  """
+  #print 'started! %s' % (multiprocessing.current_process().name)
+  pass
+
+def _task_thunk(task): # pragma: no cover
+  """Thunk for executing tasks, used by MultiProcessTaskExecutor.
+  This is called from separate processes so do not access any global state.
+
+  Args:
+    task: Task to execute.
+
+  Returns:
+    The result of the task execution. This is passed to the deferred.
+  """
+  try:
+    return task.execute()
+  except Exception as e:
+    return e
diff --git a/anvil/task_test.py b/anvil/task_test.py
new file mode 100755
index 0000000..7c54ba4
--- /dev/null
+++ b/anvil/task_test.py
@@ -0,0 +1,139 @@
+#!/usr/bin/python
+
+# Copyright 2012 Google Inc. All Rights Reserved.
+
+"""Tests for the task module.
+"""
+
+__author__ = 'benvanik@google.com (Ben Vanik)'
+
+
+import unittest2
+
+from context import BuildEnvironment
+from task import *
+from test import AsyncTestCase, FixtureTestCase
+
+
+class ExecutableTaskTest(FixtureTestCase):
+  """Behavioral tests for ExecutableTask."""
+  fixture = 'simple'
+
+  def setUp(self):
+    super(ExecutableTaskTest, self).setUp()
+    self.build_env = BuildEnvironment(root_path=self.root_path)
+
+  def testExecution(self):
+    task = ExecutableTask(self.build_env, 'cat', [
+        os.path.join(self.root_path, 'a.txt')])
+    self.assertEqual(task.execute(),
+        ('hello!\n', ''))
+
+    task = ExecutableTask(self.build_env, 'cat', [
+        os.path.join(self.root_path, 'x.txt')])
+    with self.assertRaises(ExecutableError):
+      task.execute()
+
+  def testJava(self):
+    version = JavaExecutableTask.detect_java_version()
+    self.assertNotEqual(len(version), 0)
+    self.assertIsNone(
+        JavaExecutableTask.detect_java_version(java_executable='xxx'))
+
+    # TODO(benvanik): test a JAR somehow
+    task = JavaExecutableTask(self.build_env, 'some_jar')
+
+
+class SuccessTask(Task):
+  def __init__(self, build_env, success_result, *args, **kwargs):
+    super(SuccessTask, self).__init__(build_env, *args, **kwargs)
+    self.success_result = success_result
+  def execute(self):
+    return self.success_result
+
+class FailureTask(Task):
+  def execute(self):
+    raise TypeError('Failed!')
+
+
+class TaskExecutorTest(AsyncTestCase):
+  """Behavioral tests of the TaskExecutor type."""
+
+  def runTestsWithExecutorType(self, executor_cls):
+    build_env = BuildEnvironment()
+
+    executor = executor_cls()
+    executor.close()
+    with self.assertRaises(RuntimeError):
+      executor.run_task_async(SuccessTask(build_env, True))
+    with self.assertRaises(RuntimeError):
+      executor.close()
+
+    with executor_cls() as executor:
+      d = executor.run_task_async(SuccessTask(build_env, True))
+      executor.wait(d)
+      self.assertFalse(executor.has_any_running())
+      self.assertCallbackEqual(d, True)
+      executor.close()
+      self.assertFalse(executor.has_any_running())
+
+    with executor_cls() as executor:
+      d = executor.run_task_async(FailureTask(build_env))
+      executor.wait(d)
+      self.assertFalse(executor.has_any_running())
+      self.assertErrbackWithError(d, TypeError)
+
+      d = executor.run_task_async(SuccessTask(build_env, True))
+      executor.wait(d)
+      executor.wait(d)
+      self.assertFalse(executor.has_any_running())
+      self.assertCallback(d)
+
+      da = executor.run_task_async(SuccessTask(build_env, 'a'))
+      executor.wait(da)
+      self.assertFalse(executor.has_any_running())
+      self.assertCallbackEqual(da, 'a')
+      db = executor.run_task_async(SuccessTask(build_env, 'b'))
+      executor.wait(db)
+      self.assertFalse(executor.has_any_running())
+      self.assertCallbackEqual(db, 'b')
+      dc = executor.run_task_async(SuccessTask(build_env, 'c'))
+      executor.wait(dc)
+      self.assertFalse(executor.has_any_running())
+      self.assertCallbackEqual(dc, 'c')
+
+      da = executor.run_task_async(SuccessTask(build_env, 'a'))
+      db = executor.run_task_async(SuccessTask(build_env, 'b'))
+      dc = executor.run_task_async(SuccessTask(build_env, 'c'))
+      executor.wait([da, db, dc])
+      self.assertFalse(executor.has_any_running())
+      self.assertCallbackEqual(dc, 'c')
+      self.assertCallbackEqual(db, 'b')
+      self.assertCallbackEqual(da, 'a')
+
+      da = executor.run_task_async(SuccessTask(build_env, 'a'))
+      db = executor.run_task_async(FailureTask(build_env))
+      dc = executor.run_task_async(SuccessTask(build_env, 'c'))
+      executor.wait(da)
+      self.assertCallbackEqual(da, 'a')
+      executor.wait(db)
+      self.assertErrbackWithError(db, TypeError)
+      executor.wait(dc)
+      self.assertCallbackEqual(dc, 'c')
+      self.assertFalse(executor.has_any_running())
+
+    # This test is not quite right - it's difficult to test for proper
+    # early termination
+    with executor_cls() as executor:
+      executor.close(graceful=False)
+      self.assertFalse(executor.has_any_running())
+
+  def testInProcess(self):
+    self.runTestsWithExecutorType(InProcessTaskExecutor)
+
+  def testMultiprocess(self):
+    self.runTestsWithExecutorType(MultiProcessTaskExecutor)
+
+
+if __name__ == '__main__':
+  unittest2.main()
diff --git a/anvil/test.py b/anvil/test.py
new file mode 100644
index 0000000..1023e6b
--- /dev/null
+++ b/anvil/test.py
@@ -0,0 +1,129 @@
+# Copyright 2012 Google Inc. All Rights Reserved.
+
+"""Base test case for tests that require static file fixtures.
+"""
+
+__author__ = 'benvanik@google.com (Ben Vanik)'
+
+
+import io
+import os
+import tempfile
+import shutil
+import sys
+import unittest2
+
+import util
+
+
+def main():
+  """Entry point for running tests.
+  """
+
+  # Only find test_*.py files under anvil/
+  loader = unittest2.TestLoader()
+  tests = loader.discover('anvil',
+                          pattern='*_test.py',
+                          top_level_dir='.')
+
+  # Run the tests in the default runner
+  test_runner = unittest2.runner.TextTestRunner(verbosity=2)
+  test_runner.run(tests)
+
+
+class AsyncTestCase(unittest2.TestCase):
+  """Test case adding additional asserts for async results."""
+
+  def assertCallback(self, deferred):
+    self.assertTrue(deferred.is_done())
+    done = []
+    def _callback(*args, **kwargs):
+      done.append(True)
+    def _errback(*args, **kwargs):
+      self.fail('Deferred failed when it should have succeeded')
+    deferred.add_errback_fn(_errback)
+    deferred.add_callback_fn(_callback)
+    if not len(done):
+      self.fail('Deferred not called back with success')
+
+  def assertCallbackEqual(self, deferred, value):
+    self.assertTrue(deferred.is_done())
+    done = []
+    def _callback(*args, **kwargs):
+      self.assertEqual(args[0], value)
+      done.append(True)
+    def _errback(*args, **kwargs):
+      self.fail('Deferred failed when it should have succeeded')
+    deferred.add_errback_fn(_errback)
+    deferred.add_callback_fn(_callback)
+    if not len(done):
+      self.fail('Deferred not called back with success')
+
+  def assertErrback(self, deferred):
+    self.assertTrue(deferred.is_done())
+    done = []
+    def _callback(*args, **kwargs):
+      self.fail('Deferred succeeded when it should have failed')
+    def _errback(*args, **kwargs):
+      done.append(True)
+    deferred.add_callback_fn(_callback)
+    deferred.add_errback_fn(_errback)
+    if not len(done):
+      self.fail('Deferred not called back with error')
+
+  def assertErrbackEqual(self, deferred, value):
+    self.assertTrue(deferred.is_done())
+    done = []
+    def _callback(*args, **kwargs):
+      self.fail('Deferred succeeded when it should have failed')
+    def _errback(*args, **kwargs):
+      self.assertEqual(args[0], value)
+      done.append(True)
+    deferred.add_callback_fn(_callback)
+    deferred.add_errback_fn(_errback)
+    if not len(done):
+      self.fail('Deferred not called back with error')
+
+  def assertErrbackWithError(self, deferred, error_cls):
+    self.assertTrue(deferred.is_done())
+    done = []
+    def _callback(*args, **kwargs):
+      self.fail('Deferred succeeded when it should have failed')
+    def _errback(exception=None, *args, **kwargs):
+      done.append(True)
+      self.assertIsInstance(exception, error_cls)
+    deferred.add_callback_fn(_callback)
+    deferred.add_errback_fn(_errback)
+    if not len(done):
+      self.fail('Deferred not called back with error')
+
+
+class FixtureTestCase(AsyncTestCase):
+  """Test case supporting static fixture/output support.
+  Set self.fixture to a folder name from the test/fixtures/ path.
+  """
+
+  def setUp(self):
+    super(FixtureTestCase, self).setUp()
+
+    # Root output path
+    self.temp_path = tempfile.mkdtemp()
+    self.addCleanup(shutil.rmtree, self.temp_path)
+    self.root_path = self.temp_path
+
+    # Copy fixture files
+    if self.fixture:
+      self.root_path = os.path.join(self.root_path, self.fixture)
+      build_path = util.find_build_path()
+      if not build_path:
+        raise Error('Unable to find build path')
+      fixture_path = os.path.join(
+          build_path, '..', 'test', 'fixtures', self.fixture)
+      target_path = self.temp_path + '/' + self.fixture
+      shutil.copytree(fixture_path, target_path)
+
+  def assertFileContents(self, path, contents):
+    self.assertTrue(os.path.isfile(path))
+    with io.open(path, 'rt') as f:
+      file_contents = f.read()
+    self.assertEqual(file_contents, contents)
diff --git a/anvil/util.py b/anvil/util.py
new file mode 100644
index 0000000..c016123
--- /dev/null
+++ b/anvil/util.py
@@ -0,0 +1,105 @@
+# Copyright 2012 Google Inc. All Rights Reserved.
+
+__author__ = 'benvanik@google.com (Ben Vanik)'
+
+
+import os
+import string
+import sys
+import time
+
+
+# Unfortunately there is no one-true-timer in python
+# This should always be preferred over direct use of the time module
+if sys.platform == 'win32' or sys.platform == 'cygwin':
+  timer = time.clock # pragma: no cover
+else:
+  timer = time.time # pragma: no cover
+
+
+def find_build_path(): # pragma: no cover
+  """Scans up the current path for the anvil/ folder.
+
+  Returns:
+    The 'anvil/' folder.
+  """
+  path = sys.path[0]
+  while True:
+    if os.path.exists(os.path.join(path, 'anvil')):
+      return os.path.join(path, 'anvil')
+    path = os.path.dirname(path)
+    if not len(path):
+      return None
+
+
+def is_rule_path(value):
+  """Detects whether the given value is a rule name.
+
+  Returns:
+    True if the string is a valid rule name.
+  """
+  # NOTE: in the future this could be made to support modules/etc by looking
+  #     for any valid use of ':'
+  return isinstance(value, str) and len(value) and string.find(value, ':') >= 0
+
+
+def validate_names(values, require_semicolon=False):
+  """Validates a list of rule names to ensure they are well-defined.
+
+  Args:
+    values: A list of values to validate.
+    require_semicolon: Whether to require a :
+
+  Raises:
+    NameError: A rule value is not valid.
+  """
+  if not values:
+    return
+  for value in values:
+    if not isinstance(value, str) or not len(value):
+      raise TypeError('Names must be a string of non-zero length')
+    if len(value.strip()) != len(value):
+      raise NameError(
+          'Names cannot have leading/trailing whitespace: "%s"' % (value))
+    if require_semicolon and string.find(value, ':') == -1:
+      raise NameError('Names must be a rule (contain a :): "%s"' % (value))
+
+
+def underscore_to_pascalcase(value):
+  """Converts a string from underscore_case to PascalCase.
+
+  Args:
+    value: Source string value.
+        Example - hello_world
+
+  Returns:
+    The string, converted to PascalCase.
+    Example - hello_world -> HelloWorld
+  """
+  if not value:
+    return value
+  def __CapWord(seq):
+    for word in seq:
+      yield word.capitalize()
+  return ''.join(__CapWord(word if word else '_' for word in value.split('_')))
+
+
+def which(executable_name):
+  """Gets the full path to the given executable.
+  If the given path exists in the CWD or is already absolute it is returned.
+  Otherwise this method will look through the system PATH to try to find it.
+
+  Args:
+    executable_name: Name or path to the executable.
+
+  Returns:
+    The full path to the executable or None if it was not found.
+  """
+  if (os.path.exists(executable_name) and
+      not os.path.isdir(executable_name)):
+    return os.path.abspath(executable_name)
+  for path in os.environ.get('PATH', '').split(':'):
+    if (os.path.exists(os.path.join(path, executable_name)) and
+        not os.path.isdir(os.path.join(path, executable_name))):
+      return os.path.join(path, executable_name)
+  return None
diff --git a/anvil/util_test.py b/anvil/util_test.py
new file mode 100755
index 0000000..e212eb2
--- /dev/null
+++ b/anvil/util_test.py
@@ -0,0 +1,145 @@
+#!/usr/bin/python
+
+# Copyright 2012 Google Inc. All Rights Reserved.
+
+"""Tests for the util module.
+"""
+
+__author__ = 'benvanik@google.com (Ben Vanik)'
+
+
+import unittest2
+
+import util
+
+
+class IsRulePathTest(unittest2.TestCase):
+  """Behavioral tests of the is_rule_path method."""
+
+  def testEmpty(self):
+    self.assertFalse(util.is_rule_path(None))
+    self.assertFalse(util.is_rule_path(''))
+
+  def testTypes(self):
+    self.assertFalse(util.is_rule_path(4))
+    self.assertFalse(util.is_rule_path(['a']))
+    self.assertFalse(util.is_rule_path({'a': 1}))
+
+  def testNames(self):
+    self.assertTrue(util.is_rule_path(':a'))
+    self.assertTrue(util.is_rule_path(':ab'))
+    self.assertTrue(util.is_rule_path('xx:ab'))
+    self.assertTrue(util.is_rule_path('/a/b:ab'))
+
+    self.assertFalse(util.is_rule_path('a'))
+    self.assertFalse(util.is_rule_path('/a/b.c'))
+    self.assertFalse(util.is_rule_path('a b c'))
+
+
+class ValidateNamesTest(unittest2.TestCase):
+  """Behavioral tests of the validate_names method."""
+
+  def testEmpty(self):
+    util.validate_names(None)
+    util.validate_names([])
+
+  def testNames(self):
+    util.validate_names(['a'])
+    util.validate_names([':a'])
+    util.validate_names(['xx:a'])
+    util.validate_names(['/a/b:a'])
+    util.validate_names(['/a/b.c:a'])
+    util.validate_names(['/a/b.c/:a'])
+    util.validate_names(['a', ':b'])
+    with self.assertRaises(TypeError):
+      util.validate_names([None])
+    with self.assertRaises(TypeError):
+      util.validate_names([''])
+    with self.assertRaises(TypeError):
+      util.validate_names([{}])
+    with self.assertRaises(NameError):
+      util.validate_names([' a'])
+    with self.assertRaises(NameError):
+      util.validate_names(['a '])
+    with self.assertRaises(NameError):
+      util.validate_names([' a '])
+    with self.assertRaises(NameError):
+      util.validate_names(['a', ' b'])
+
+  def testRequireSemicolon(self):
+    util.validate_names([':a'], require_semicolon=True)
+    util.validate_names([':a', ':b'], require_semicolon=True)
+    with self.assertRaises(NameError):
+      util.validate_names(['a'], require_semicolon=True)
+    with self.assertRaises(NameError):
+      util.validate_names([':a', 'b'], require_semicolon=True)
+
+
+class UnderscoreToPascalCaseTest(unittest2.TestCase):
+  """Behavioral tests of the underscore_to_pascalcase method."""
+
+  def testEmpty(self):
+    self.assertEqual(
+        util.underscore_to_pascalcase(None),
+        None)
+    self.assertEqual(
+        util.underscore_to_pascalcase(''),
+        '')
+
+  def testUnderscores(self):
+    self.assertEqual(
+        util.underscore_to_pascalcase('ab'),
+        'Ab')
+    self.assertEqual(
+        util.underscore_to_pascalcase('aB'),
+        'Ab')
+    self.assertEqual(
+        util.underscore_to_pascalcase('AB'),
+        'Ab')
+    self.assertEqual(
+        util.underscore_to_pascalcase('a_b'),
+        'AB')
+    self.assertEqual(
+        util.underscore_to_pascalcase('A_b'),
+        'AB')
+    self.assertEqual(
+        util.underscore_to_pascalcase('aa_bb'),
+        'AaBb')
+    self.assertEqual(
+        util.underscore_to_pascalcase('aa1_bb2'),
+        'Aa1Bb2')
+    self.assertEqual(
+        util.underscore_to_pascalcase('1aa_2bb'),
+        '1aa2bb')
+
+  def testWhitespace(self):
+    self.assertEqual(
+        util.underscore_to_pascalcase(' '),
+        ' ')
+    self.assertEqual(
+        util.underscore_to_pascalcase(' a'),
+        ' a')
+    self.assertEqual(
+        util.underscore_to_pascalcase('a '),
+        'A ')
+    self.assertEqual(
+        util.underscore_to_pascalcase(' a '),
+        ' a ')
+    self.assertEqual(
+        util.underscore_to_pascalcase('a b'),
+        'A b')
+    self.assertEqual(
+        util.underscore_to_pascalcase('a  b'),
+        'A  b')
+
+class WhichTest(unittest2.TestCase):
+  """Behavioral tests of the which method."""
+
+  def test(self):
+    self.assertEqual(util.which('/bin/sh'), '/bin/sh')
+    self.assertIsNone(util.which('xxx'))
+    self.assertIsNotNone(util.which('cat'))
+
+
+if __name__ == '__main__':
+  unittest2.main()
diff --git a/anvil/version.py b/anvil/version.py
new file mode 100644
index 0000000..1a4f8ba
--- /dev/null
+++ b/anvil/version.py
@@ -0,0 +1,11 @@
+# Copyright 2012 Google Inc. All Rights Reserved.
+
+"""
+"""
+
+__author__ = 'benvanik@google.com (Ben Vanik)'
+
+
+# TODO(benvanik): pull from somewhere?
+VERSION = (0, 0, 0, 1)
+VERSION_STR = '0.0.0.1'
diff --git a/run-coverage.sh b/run-coverage.sh
new file mode 100755
index 0000000..5994fe0
--- /dev/null
+++ b/run-coverage.sh
@@ -0,0 +1,38 @@
+#!/bin/bash
+
+# Copyright 2012 Google Inc. All Rights Reserved.
+
+# This script runs the build unit tests with a coverage run and spits out
+# the result HTML to scratch/coverage/
+
+# TODO(benvanik): merge with run-tests.py?
+
+# This must currently run from the root of the repo
+# TODO(benvanik): make this runnable from anywhere (find git directory?)
+if [ ! -d ".git" ]; then
+  echo "This script must be run from the root of the repository (the folder containing .git)"
+  exit 1
+fi
+
+# Get into a known-good initial state by removing everything
+# (removes the possibility for confusing old output when runs fail)
+if [ -e ".coverage" ]; then
+  rm .coverage
+fi
+if [ -d "scratch/coverage" ]; then
+  rm -rf scratch/coverage
+fi
+
+# Run all unit tests with coverage
+coverage run --branch ./run-tests.py
+
+# Dump to console (so you see *something*)
+coverage report -m
+
+# Output HTML report
+coverage html -d scratch/coverage/
+
+# Cleanup the coverage temp data, as it's unused and regenerated
+if [ -e ".coverage" ]; then
+  rm .coverage
+fi
diff --git a/run-tests.py b/run-tests.py
new file mode 100755
index 0000000..b354811
--- /dev/null
+++ b/run-tests.py
@@ -0,0 +1,21 @@
+#!/usr/bin/python
+
+# Copyright 2012 Google Inc. All Rights Reserved.
+
+"""Python build system test runner.
+In order to speed things up (and avoid some platform incompatibilities) this
+script should be used instead of unit2 or python -m unittest.
+"""
+
+__author__ = 'benvanik@google.com (Ben Vanik)'
+
+
+import os
+import sys
+
+# Add self to the root search path
+sys.path.insert(0, os.path.abspath(os.path.dirname(__file__)))
+
+# Run the tests
+import anvil.test
+anvil.test.main()
diff --git a/setup.py b/setup.py
new file mode 100755
index 0000000..8bc0afe
--- /dev/null
+++ b/setup.py
@@ -0,0 +1,67 @@
+#!/usr/bin/env python
+
+# Copyright 2012 Google Inc. All Rights Reserved.
+
+"""
+Anvil
+-----
+
+A parallel build system and content pipeline.
+
+"""
+
+__author__ = 'benvanik@google.com (Ben Vanik)'
+
+
+import sys
+from setuptools import setup
+
+
+# Require Python 2.6+
+if sys.hexversion < 0x02060000:
+  raise RuntimeError('Python 2.6.0 or higher required')
+
+
+setup(
+    name='Anvil',
+    version='0.0.1dev',
+    url='https://github.com/benvanik/anvil-build/',
+    download_url='https://github.com/benvanik/anvil-build/tarball/master',
+    license='Apache',
+    author='Ben Vanik',
+    author_email='benvanik@google.com',
+    description='A parallel build system and content pipeline',
+    long_description=__doc__,
+    platforms='any',
+    install_requires=[
+        'argparse>=1.2.1',
+        'autobahn>=0.5.1',
+        'coverage>=3.5.1',
+        'glob2>=0.3',
+        'networkx>=1.6',
+        'Sphinx>=1.1.3',
+        'watchdog>=0.6',
+        'unittest2>=0.5.1',
+        ],
+    packages=['anvil',],
+    test_suite='anvil.test',
+    include_package_data=True,
+    zip_safe=True,
+    entry_points = {
+        'console_scripts': [
+            'anvil = anvil.manage:main',
+            ],
+        },
+    classifiers=[
+        'Development Status :: 3 - Alpha',
+        'Environment :: Console',
+        'Intended Audience :: Developers',
+        'License :: OSI Approved :: Apache Software License',
+        'Operating System :: OS Independent',
+        'Programming Language :: Python',
+        'Programming Language :: Python :: 2.6',
+        'Programming Language :: Python :: 2.7',
+        'Topic :: Software Development :: Libraries :: Python Modules',
+        'Topic :: Utilities',
+        ])
+
diff --git a/test/fixtures/core_rules/concat_files/1.txt b/test/fixtures/core_rules/concat_files/1.txt
new file mode 100644
index 0000000..d00491f
--- /dev/null
+++ b/test/fixtures/core_rules/concat_files/1.txt
@@ -0,0 +1 @@
+1
diff --git a/test/fixtures/core_rules/concat_files/2.txt b/test/fixtures/core_rules/concat_files/2.txt
new file mode 100644
index 0000000..0cfbf08
--- /dev/null
+++ b/test/fixtures/core_rules/concat_files/2.txt
@@ -0,0 +1 @@
+2
diff --git a/test/fixtures/core_rules/concat_files/3.txt b/test/fixtures/core_rules/concat_files/3.txt
new file mode 100644
index 0000000..00750ed
--- /dev/null
+++ b/test/fixtures/core_rules/concat_files/3.txt
@@ -0,0 +1 @@
+3
diff --git a/test/fixtures/core_rules/concat_files/4.txt b/test/fixtures/core_rules/concat_files/4.txt
new file mode 100644
index 0000000..b8626c4
--- /dev/null
+++ b/test/fixtures/core_rules/concat_files/4.txt
@@ -0,0 +1 @@
+4
diff --git a/test/fixtures/core_rules/concat_files/BUILD b/test/fixtures/core_rules/concat_files/BUILD
new file mode 100644
index 0000000..c4e1c0c
--- /dev/null
+++ b/test/fixtures/core_rules/concat_files/BUILD
@@ -0,0 +1,17 @@
+concat_files(
+    name='concat',
+    srcs=['1.txt', '2.txt', '3.txt', '4.txt'])
+
+concat_files(
+    name='concat_out',
+    srcs=['1.txt', '2.txt', '3.txt', '4.txt'],
+    out='concat.txt')
+
+concat_files(
+    name='concat_template',
+    srcs=[':concat_out', 't.txt', ':concat_out'])
+template_files(
+    name='templated',
+    srcs=[':concat_template',],
+    new_extension='.out',
+    params={'hello': 'world!'})
diff --git a/test/fixtures/core_rules/concat_files/t.txt b/test/fixtures/core_rules/concat_files/t.txt
new file mode 100644
index 0000000..cbc9ec2
--- /dev/null
+++ b/test/fixtures/core_rules/concat_files/t.txt
@@ -0,0 +1 @@
+x${hello}x
diff --git a/test/fixtures/core_rules/copy_files/BUILD b/test/fixtures/core_rules/copy_files/BUILD
new file mode 100644
index 0000000..7ca74fb
--- /dev/null
+++ b/test/fixtures/core_rules/copy_files/BUILD
@@ -0,0 +1,4 @@
+file_set('a', srcs='a.txt')
+file_set('all_txt', srcs=glob('**/*.txt'))
+
+copy_files('copy_all_txt', srcs=':all_txt')
diff --git a/test/fixtures/core_rules/copy_files/a.txt b/test/fixtures/core_rules/copy_files/a.txt
new file mode 100644
index 0000000..7898192
--- /dev/null
+++ b/test/fixtures/core_rules/copy_files/a.txt
@@ -0,0 +1 @@
+a
diff --git a/test/fixtures/core_rules/copy_files/dir/BUILD b/test/fixtures/core_rules/copy_files/dir/BUILD
new file mode 100644
index 0000000..a2c2e64
--- /dev/null
+++ b/test/fixtures/core_rules/copy_files/dir/BUILD
@@ -0,0 +1,4 @@
+file_set('b', srcs='b.txt')
+file_set('c', srcs='c.not-txt')
+
+copy_files('copy_c', srcs=':c')
diff --git a/test/fixtures/core_rules/copy_files/dir/b.txt b/test/fixtures/core_rules/copy_files/dir/b.txt
new file mode 100644
index 0000000..6178079
--- /dev/null
+++ b/test/fixtures/core_rules/copy_files/dir/b.txt
@@ -0,0 +1 @@
+b
diff --git a/test/fixtures/core_rules/copy_files/dir/c.not-txt b/test/fixtures/core_rules/copy_files/dir/c.not-txt
new file mode 100644
index 0000000..f2ad6c7
--- /dev/null
+++ b/test/fixtures/core_rules/copy_files/dir/c.not-txt
@@ -0,0 +1 @@
+c
diff --git a/test/fixtures/core_rules/file_set/BUILD b/test/fixtures/core_rules/file_set/BUILD
new file mode 100644
index 0000000..7c43a51
--- /dev/null
+++ b/test/fixtures/core_rules/file_set/BUILD
@@ -0,0 +1,9 @@
+file_set('a', srcs='a.txt')
+file_set('a_glob', srcs=glob('*.txt'))
+
+file_set('b_ref', srcs='dir:b')
+
+file_set('all_glob', srcs=glob('**/*.txt'))
+
+file_set('combo', srcs=[':a', ':b_ref'])
+file_set('dupes', srcs=[':a', 'a.txt', ':b_ref', 'dir:b', ':combo'])
diff --git a/test/fixtures/core_rules/file_set/a.txt b/test/fixtures/core_rules/file_set/a.txt
new file mode 100644
index 0000000..7898192
--- /dev/null
+++ b/test/fixtures/core_rules/file_set/a.txt
@@ -0,0 +1 @@
+a
diff --git a/test/fixtures/core_rules/file_set/dir/BUILD b/test/fixtures/core_rules/file_set/dir/BUILD
new file mode 100644
index 0000000..ad31421
--- /dev/null
+++ b/test/fixtures/core_rules/file_set/dir/BUILD
@@ -0,0 +1,2 @@
+file_set('b', srcs='b.txt')
+file_set('b_glob', srcs=glob('*.txt'))
diff --git a/test/fixtures/core_rules/file_set/dir/b.txt b/test/fixtures/core_rules/file_set/dir/b.txt
new file mode 100644
index 0000000..6178079
--- /dev/null
+++ b/test/fixtures/core_rules/file_set/dir/b.txt
@@ -0,0 +1 @@
+b
diff --git a/test/fixtures/core_rules/template_files/BUILD b/test/fixtures/core_rules/template_files/BUILD
new file mode 100644
index 0000000..5f4198b
--- /dev/null
+++ b/test/fixtures/core_rules/template_files/BUILD
@@ -0,0 +1,25 @@
+file_set('a', srcs='a.txt')
+template_files(
+    name='template_a',
+    srcs='a.txt',
+    params={'hello': 'world_a',})
+template_files(
+    name='template_a_rule',
+    srcs=':a',
+    params={'hello': 'world_a_rule',})
+
+file_set('all_glob', srcs=glob('**/*.txt'))
+template_files(
+    name='template_all',
+    srcs=':all_glob',
+    params={'hello': 'world',})
+
+template_files(
+    name='template_dep_1',
+    srcs=glob('**/*.nfo'),
+    params={'arg1': '${arg2}',})
+template_files(
+    name='template_dep_2',
+    srcs=':template_dep_1',
+    new_extension='.out',
+    params={'arg2': 'world!',})
diff --git a/test/fixtures/core_rules/template_files/a.nfo b/test/fixtures/core_rules/template_files/a.nfo
new file mode 100644
index 0000000..8e6e9c5
--- /dev/null
+++ b/test/fixtures/core_rules/template_files/a.nfo
@@ -0,0 +1 @@
+123${arg1}456
diff --git a/test/fixtures/core_rules/template_files/a.txt b/test/fixtures/core_rules/template_files/a.txt
new file mode 100644
index 0000000..06d5f9c
--- /dev/null
+++ b/test/fixtures/core_rules/template_files/a.txt
@@ -0,0 +1 @@
+123${hello}456
diff --git a/test/fixtures/core_rules/template_files/dir/BUILD b/test/fixtures/core_rules/template_files/dir/BUILD
new file mode 100644
index 0000000..44725fe
--- /dev/null
+++ b/test/fixtures/core_rules/template_files/dir/BUILD
@@ -0,0 +1,9 @@
+file_set('b', srcs='b.txt')
+template_files(
+    name='template_b',
+    srcs='b.txt',
+    params={'hello': 'world_b',})
+template_files(
+    name='template_b_rule',
+    srcs=':b',
+    params={'hello': 'world_b_rule',})
diff --git a/test/fixtures/core_rules/template_files/dir/b.nfo b/test/fixtures/core_rules/template_files/dir/b.nfo
new file mode 100644
index 0000000..076a131
--- /dev/null
+++ b/test/fixtures/core_rules/template_files/dir/b.nfo
@@ -0,0 +1 @@
+b123${arg1}456
diff --git a/test/fixtures/core_rules/template_files/dir/b.txt b/test/fixtures/core_rules/template_files/dir/b.txt
new file mode 100644
index 0000000..d7ca613
--- /dev/null
+++ b/test/fixtures/core_rules/template_files/dir/b.txt
@@ -0,0 +1 @@
+b123${hello}456
diff --git a/test/fixtures/manage/bad_commands/bad_commands.py b/test/fixtures/manage/bad_commands/bad_commands.py
new file mode 100644
index 0000000..665a7d4
--- /dev/null
+++ b/test/fixtures/manage/bad_commands/bad_commands.py
@@ -0,0 +1,12 @@
+from anvil.manage import manage_command
+
+
+@manage_command('test_command')
+def test_command(args, cwd):
+  return 0
+
+
+# Duplicate name
+@manage_command('test_command')
+def test_command1(args, cwd):
+  return 0
diff --git a/test/fixtures/manage/commands/test_commands.py b/test/fixtures/manage/commands/test_commands.py
new file mode 100644
index 0000000..f10fa92
--- /dev/null
+++ b/test/fixtures/manage/commands/test_commands.py
@@ -0,0 +1,6 @@
+from anvil.manage import manage_command
+
+
+@manage_command('test_command')
+def test_command(args, cwd):
+  return 123
diff --git a/test/fixtures/resolution/BUILD b/test/fixtures/resolution/BUILD
new file mode 100644
index 0000000..c4301c0
--- /dev/null
+++ b/test/fixtures/resolution/BUILD
@@ -0,0 +1 @@
+file_set('root_rule', deps=['a:rule_a'])
diff --git a/test/fixtures/resolution/a/BUILD b/test/fixtures/resolution/a/BUILD
new file mode 100644
index 0000000..077f0c8
--- /dev/null
+++ b/test/fixtures/resolution/a/BUILD
@@ -0,0 +1 @@
+file_set('rule_a', deps=['../b:rule_b'])
diff --git a/test/fixtures/resolution/b/BUILD b/test/fixtures/resolution/b/BUILD
new file mode 100644
index 0000000..91c00d4
--- /dev/null
+++ b/test/fixtures/resolution/b/BUILD
@@ -0,0 +1 @@
+file_set('rule_b', deps=['c:rule_c'])
diff --git a/test/fixtures/resolution/b/c/BUILD b/test/fixtures/resolution/b/c/BUILD
new file mode 100644
index 0000000..2a5215a
--- /dev/null
+++ b/test/fixtures/resolution/b/c/BUILD
@@ -0,0 +1 @@
+file_set('rule_c', deps=['build_file.py:rule_c_file'])
diff --git a/test/fixtures/resolution/b/c/build_file.py b/test/fixtures/resolution/b/c/build_file.py
new file mode 100644
index 0000000..0375dbe
--- /dev/null
+++ b/test/fixtures/resolution/b/c/build_file.py
@@ -0,0 +1 @@
+file_set('rule_c_file')
diff --git a/test/fixtures/resolution/empty/dummy b/test/fixtures/resolution/empty/dummy
new file mode 100644
index 0000000..45b983b
--- /dev/null
+++ b/test/fixtures/resolution/empty/dummy
@@ -0,0 +1 @@
+hi
diff --git a/test/fixtures/rules/dummy_rules.py b/test/fixtures/rules/dummy_rules.py
new file mode 100644
index 0000000..b74c9ee
--- /dev/null
+++ b/test/fixtures/rules/dummy_rules.py
@@ -0,0 +1,16 @@
+# Dummy rule types for testing rules
+
+
+from anvil.rule import Rule, build_rule
+
+
+@build_rule('rule_a')
+class RuleA(Rule):
+  def __init__(self, name, *args, **kwargs):
+    super(RuleA, self).__init__(name, *args, **kwargs)
+
+
+@build_rule('rule_b')
+class RuleB(Rule):
+  def __init__(self, name, *args, **kwargs):
+    super(RuleB, self).__init__(name, *args, **kwargs)
diff --git a/test/fixtures/rules/dupe.py b/test/fixtures/rules/dupe.py
new file mode 100644
index 0000000..3582869
--- /dev/null
+++ b/test/fixtures/rules/dupe.py
@@ -0,0 +1,16 @@
+# File with duplicate rules
+
+
+from anvil.rule import Rule, build_rule
+
+
+@build_rule('rule_d')
+class RuleD1(Rule):
+  def __init__(self, name, *args, **kwargs):
+    super(RuleD1, self).__init__(name, *args, **kwargs)
+
+
+@build_rule('rule_d')
+class RuleD2(Rule):
+  def __init__(self, name, *args, **kwargs):
+    super(RuleD2, self).__init__(name, *args, **kwargs)
diff --git a/test/fixtures/rules/more/more_rules.py b/test/fixtures/rules/more/more_rules.py
new file mode 100644
index 0000000..e39a915
--- /dev/null
+++ b/test/fixtures/rules/more/more_rules.py
@@ -0,0 +1,10 @@
+# More (nested) rule types for testing rules
+
+
+from anvil.rule import Rule, build_rule
+
+
+@build_rule('rule_c')
+class RuleC(Rule):
+  def __init__(self, name, *args, **kwargs):
+    super(RuleC, self).__init__(name, *args, **kwargs)
diff --git a/test/fixtures/rules/rule_x.py b/test/fixtures/rules/rule_x.py
new file mode 100644
index 0000000..ec606db
--- /dev/null
+++ b/test/fixtures/rules/rule_x.py
@@ -0,0 +1,10 @@
+# Dummy file - this rule should not be discovered
+
+
+from anvil.rule import Rule, build_rule
+
+
+@build_rule('rule_x')
+class RuleX(Rule):
+  def __init__(self, name, *args, **kwargs):
+    super(RuleX, self).__init__(name, *args, **kwargs)
diff --git a/test/fixtures/simple/BUILD b/test/fixtures/simple/BUILD
new file mode 100644
index 0000000..98bfc27
--- /dev/null
+++ b/test/fixtures/simple/BUILD
@@ -0,0 +1,37 @@
+# Simple sample build file
+# Does nothing but provide some rules
+
+file_set('a',
+     srcs=['a.txt'])
+
+file_set('b',
+    srcs=['b.txt'])
+
+file_set('c',
+    srcs=['c.txt'],
+    deps=[':a', ':b'])
+
+file_set('local_txt',
+    srcs=glob('*.txt'))
+file_set('recursive_txt',
+    srcs=glob('**/*.txt'))
+file_set('missing_txt',
+    srcs='x.txt')
+file_set('missing_glob_txt',
+    srcs=glob('*.notpresent'))
+
+file_set('local_txt_filter',
+    srcs=glob('*'),
+    src_filter='*.txt')
+file_set('recursive_txt_filter',
+    srcs=glob('**/*'),
+    src_filter='*.txt')
+
+file_set('file_input',
+    srcs='a.txt')
+file_set('rule_input',
+    srcs=':file_input')
+file_set('mixed_input',
+    srcs=['b.txt', ':file_input'])
+file_set('missing_input',
+    srcs=':x')
diff --git a/test/fixtures/simple/a.txt b/test/fixtures/simple/a.txt
new file mode 100644
index 0000000..4effa19
--- /dev/null
+++ b/test/fixtures/simple/a.txt
@@ -0,0 +1 @@
+hello!
diff --git a/test/fixtures/simple/b.txt b/test/fixtures/simple/b.txt
new file mode 100644
index 0000000..18df798
--- /dev/null
+++ b/test/fixtures/simple/b.txt
@@ -0,0 +1 @@
+world!
diff --git a/test/fixtures/simple/c.txt b/test/fixtures/simple/c.txt
new file mode 100644
index 0000000..6f1de24
--- /dev/null
+++ b/test/fixtures/simple/c.txt
@@ -0,0 +1 @@
+!!!
diff --git a/test/fixtures/simple/dir/dir_2/BUILD b/test/fixtures/simple/dir/dir_2/BUILD
new file mode 100644
index 0000000..b2c3e9b
--- /dev/null
+++ b/test/fixtures/simple/dir/dir_2/BUILD
@@ -0,0 +1 @@
+file_set('d',srcs=['d.txt'])
diff --git a/test/fixtures/simple/dir/dir_2/d.txt b/test/fixtures/simple/dir/dir_2/d.txt
new file mode 100644
index 0000000..6f1de24
--- /dev/null
+++ b/test/fixtures/simple/dir/dir_2/d.txt
@@ -0,0 +1 @@
+!!!
diff --git a/test/fixtures/simple/dir/dir_2/e.txt b/test/fixtures/simple/dir/dir_2/e.txt
new file mode 100644
index 0000000..6f1de24
--- /dev/null
+++ b/test/fixtures/simple/dir/dir_2/e.txt
@@ -0,0 +1 @@
+!!!
diff --git a/test/fixtures/simple/dir/dir_2/f.not-txt b/test/fixtures/simple/dir/dir_2/f.not-txt
new file mode 100644
index 0000000..6f1de24
--- /dev/null
+++ b/test/fixtures/simple/dir/dir_2/f.not-txt
@@ -0,0 +1 @@
+!!!
diff --git a/test/fixtures/simple/g.not-txt b/test/fixtures/simple/g.not-txt
new file mode 100644
index 0000000..6f1de24
--- /dev/null
+++ b/test/fixtures/simple/g.not-txt
@@ -0,0 +1 @@
+!!!