Turns out e2e just works, but let's prove that (and note that we're not completely efficient here, we send all msgs that get routed to the exchanges bound to the federation exchange, regardless of whether they get routed anywhere after that).

deps/rabbitmq_federation/TODO

@@ -6,7 +6,7 @@ Test / fix with alternate PLAIN creds
 Allow use of EXTERNAL etc
 Be smarter about bind / unbind
 Deal with downstream going down
-Figure out how e2e interacts with this
+Figure out if there's a more efficient way to make e2e work with this.
 Remove that ETS table
 
 ---

deps/rabbitmq_federation/test/rabbit_federation_test.erl

@@ -82,6 +82,23 @@ multiple_downstreams_test() ->
               delete_exchange(Ch, <<"upstream2">>)
       end).
 
+e2e_test() ->
+    with_ch(
+      fun (Ch) ->
+              declare_exchange(Ch, <<"upstream">>, <<"fanout">>),
+              declare_fed_exchange(Ch, <<"downstream1">>,
+                                   [<<"amqp://localhost/%2f/upstream">>],
+                                   <<"fanout">>),
+              declare_exchange(Ch, <<"downstream2">>, <<"direct">>),
+              bind_exchange(Ch, <<"downstream2">>, <<"downstream1">>, <<"">>),
+              Q = bind_queue(Ch, <<"downstream2">>, <<"key">>),
+              publish_expect(Ch, <<"upstream">>, <<"key">>, Q, <<"HELLO1">>),
+              delete_exchange(Ch, <<"downstream1">>),
+              delete_exchange(Ch, <<"downstream2">>),
+              delete_exchange(Ch, <<"upstream">>)
+      end).
+
+
 %% Downstream: port 5672, has federation
 %% Upstream:   port 5673, may not have federation
 
@@ -148,12 +165,24 @@ declare_exchange(Ch, X, Type) ->
                                                type     = Type,
                                                durable  = true}).
 
-bind_queue(Ch, X, Key) ->
+declare_queue(Ch) ->
     #'queue.declare_ok'{ queue = Q } =
         amqp_channel:call(Ch, #'queue.declare'{ exclusive = true }),
+    Q.
+
+bind_queue(Ch, Q, X, Key) ->
     amqp_channel:call(Ch, #'queue.bind'{ queue       = Q,
                                          exchange    = X,
-                                         routing_key = Key }),
+                                         routing_key = Key }).
+
+bind_exchange(Ch, D, S, Key) ->
+    amqp_channel:call(Ch, #'exchange.bind'{ destination = D,
+                                            source      = S,
+                                            routing_key = Key }).
+
+bind_queue(Ch, X, Key) ->
+    Q = declare_queue(Ch),
+    bind_queue(Ch, Q, X, Key),
     Q.
 
 delete_exchange(Ch, X) ->