gitlab-ce/doc/development/testing_guide/end_to_end/page_objects.md

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Page objects in GitLab QA

In GitLab QA we are using a known pattern, called Page Objects.

This means that we have built an abstraction for all pages in GitLab that we use to drive GitLab QA scenarios. Whenever we do something on a page, like filling in a form or clicking a button, we do that only through a page object associated with this area of GitLab.

For example, when GitLab QA test harness signs in into GitLab, it needs to fill in user login and user password. To do that, we have a class, called Page::Main::Login and sign_in_using_credentials methods, that is the only piece of the code, that reads the user_login and user_password fields.

Why do we need that?

We need page objects because we need to reduce duplication and avoid problems whenever someone changes some selectors in GitLab's source code.

Imagine that we have a hundred specs in GitLab QA, and we need to sign into GitLab each time, before we make assertions. Without a page object, one would need to rely on volatile helpers or invoke Capybara methods directly. Imagine invoking fill_in :user_login in every *_spec.rb file / test example.

When someone later changes t.text_field :login in the view associated with this page to t.text_field :username it generates a different field identifier, what would effectively break all tests.

Because we are using Page::Main::Login.perform(&:sign_in_using_credentials) everywhere, when we want to sign in to GitLab, the page object is the single source of truth, and we must update fill_in :user_login to fill_in :user_username only in one place.

What problems did we have in the past?

We do not run QA tests for every commit, because of performance reasons, and the time it would take to build packages and test everything.

That is why when someone changes t.text_field :login to t.text_field :username in the new session view we don't know about this change until our GitLab QA nightly pipeline fails, or until someone triggers package-and-qa action in their merge request.

Such a change would break all tests. We call this problem a fragile tests problem.

To make GitLab QA more reliable and robust, we had to solve this problem by introducing coupling between GitLab CE / EE views and GitLab QA.

How did we solve fragile tests problem?

Currently, when you add a new Page::Base derived class, you must also define all selectors that your page objects depend on.

Whenever you push your code to CE / EE repository, qa:selectors sanity test job runs as a part of a CI pipeline.

This test validates all page objects that we have implemented in qa/page directory. When it fails, it notifies you about missing or invalid views/selectors definition.

How to properly implement a page object?

We have built a DSL to define coupling between a page object and GitLab views it is actually implemented by. See an example below.

module Page
  module Main
    class Login < Page::Base
      view 'app/views/devise/passwords/edit.html.haml' do
        element :password_field
        element :password_confirmation
        element :change_password_button
      end

      view 'app/views/devise/sessions/_new_base.html.haml' do
        element :login_field
        element :password_field
        element :sign_in_button
      end

      # ...
    end
  end
end

Defining Elements

The view DSL method corresponds to the Rails view, partial, or Vue component that renders the elements.

The element DSL method in turn declares an element for which a corresponding data-qa-selector=element_name_snaked data attribute must be added to the view file.

You can also define a value (String or Regexp) to match to the actual view code but this is deprecated in favor of the above method for two reasons:

• Consistency: there is only one way to define an element
• Separation of concerns: QA uses dedicated data-qa-* attributes instead of reusing code or classes used by other components (e.g. js-* classes etc.)

view 'app/views/my/view.html.haml' do

  ### Good ###

  # Implicitly require the CSS selector `[data-qa-selector="logout_button"]` to be present in the view
  element :logout_button

  ### Bad ###

  ## This is deprecated and forbidden by the `QA/ElementWithPattern` RuboCop cop.
  # Require `f.submit "Sign in"` to be present in `my/view.html.haml
  element :my_button, 'f.submit "Sign in"' # rubocop:disable QA/ElementWithPattern

  ## This is deprecated and forbidden by the `QA/ElementWithPattern` RuboCop cop.
  # Match every line in `my/view.html.haml` against
  # `/link_to .* "My Profile"/` regexp.
  element :profile_link, /link_to .* "My Profile"/ # rubocop:disable QA/ElementWithPattern
end

Adding Elements to a View

Given the following elements...

view 'app/views/my/view.html.haml' do
  element :login_field
  element :password_field
  element :sign_in_button
end

To add these elements to the view, you must change the Rails view, partial, or Vue component by adding a data-qa-selector attribute for each element defined.

In our case, data-qa-selector="login_field", data-qa-selector="password_field" and data-qa-selector="sign_in_button"

app/views/my/view.html.haml

= f.text_field :login, class: "form-control top", autofocus: "autofocus", autocapitalize: "off", autocorrect: "off", required: true, title: "This field is required.", data: { qa_selector: 'login_field' }
= f.password_field :password, class: "form-control bottom", required: true, title: "This field is required.", data: { qa_selector: 'password_field' }
= f.submit "Sign in", class: "btn btn-success", data: { qa_selector: 'sign_in_button' }

Things to note:

• The name of the element and the qa_selector must match and be snake_cased
• If the element appears on the page unconditionally, add required: true to the element. See Dynamic element validation
• You may see .qa-selector classes in existing Page Objects. We should prefer the data-qa-selector method of definition over the .qa-selector CSS class

data-qa-selector vs .qa-selector

Introduced in GitLab 12.1

There are two supported methods of defining elements within a view.

1. data-qa-selector attribute
2. .qa-selector class

Any existing .qa-selector class should be considered deprecated and we should prefer the data-qa-selector method of definition.

Dynamic element selection

Introduced in GitLab 12.5

A common occurrence in automated testing is selecting a single "one-of-many" element. In a list of several items, how do you differentiate what you are selecting on? The most common workaround for this is via text matching. Instead, a better practice is by matching on that specific element by a unique identifier, rather than by text.

We got around this by adding the data-qa-* extensible selection mechanism.

Examples

Example 1

Given the following Rails view (using GitLab Issues as an example):

%ul.issues-list
 - @issues.each do |issue|
   %li.issue{data: { qa_selector: 'issue', qa_issue_title: issue.title } }= link_to issue

We can select on that specific issue by matching on the Rails model.

class Page::Project::Issues::Index < Page::Base
  def has_issue?(issue)
    has_element? :issue, issue_title: issue
  end
end

In our test, we can validate that this particular issue exists.

describe 'Issue' do
  it 'has an issue titled "hello"' do
    Page::Project::Issues::Index.perform do |index|
      expect(index).to have_issue('hello')
    end
  end
end

Example 2

By an index...

%ol
  - @some_model.each_with_index do |model, idx|
    %li.model{ data: { qa_selector: 'model', qa_index: idx } }

expect(the_page).to have_element(:model, index: 1) #=> select on the first model that appears in the list

Exceptions

In some cases, it might not be possible or worthwhile to add a selector.

Some UI components use external libraries, including some maintained by third parties. Even if a library is maintained by GitLab, the selector sanity test only runs on code within the GitLab project, so it's not possible to specify the path for the view for code in a library.

In such rare cases it's reasonable to use CSS selectors in page object methods, with a comment explaining why an element can't be added.

Define Page concerns

Some pages share common behaviors, and/or are prepended with EE-specific modules that adds EE-specific methods.

These modules must:

1. Extend from the QA::Page::PageConcern module, with extend QA::Page::PageConcern.
2. Override the self.prepended method if they need to include/prepend other modules themselves, and/or define view or elements.
3. Call super as the first thing in self.prepended.
4. Include/prepend other modules and define their view/elements in a base.class_eval block to ensure they're defined in the class that prepends the module.

These steps ensure the sanity selectors check detect problems properly.

For example, qa/qa/ee/page/merge_request/show.rb adds EE-specific methods to qa/qa/page/merge_request/show.rb (with QA::Page::MergeRequest::Show.prepend_if_ee('QA::EE::Page::MergeRequest::Show')) and following is how it's implemented (only showing the relevant part and referring to the 4 steps described above with inline comments):

module QA
  module EE
    module Page
      module MergeRequest
        module Show
          extend QA::Page::PageConcern # 1.

          def self.prepended(base) # 2.
            super # 3.

            base.class_eval do # 4.
              prepend Page::Component::LicenseManagement

              view 'app/assets/javascripts/vue_merge_request_widget/components/states/sha_mismatch.vue' do
                element :head_mismatch, "The source branch HEAD has recently changed."
              end

              [...]
            end
          end
        end
      end
    end
  end
end

Running the test locally

During development, you can run the qa:selectors test by running

bin/qa Test::Sanity::Selectors

from within the qa directory.

Where to ask for help?

If you need more information, ask for help on #quality channel on Slack (internal, GitLab Team only).

If you are not a Team Member, and you still need help to contribute, please open an issue in GitLab CE issue tracker with the ~QA label.