Resource classes in GitLab QA

Resources are primarily created using Browser UI steps, but can also be created via the API or the CLI.

A typical resource class is used to create a new resource that can be used in a single test. However, several tests can end up creating the same kind of resource and use it in ways that mean it could have been used by more than one test. Creating a new resource each time is not efficient. Therefore, we can also create reusable resources that are created once and can then be used by many tests.

In the following section the content focuses on single-use resources, however it also applies to reusable resources. Information specific to reusable resources is detailed below.

How to properly implement a resource class?

All non-reusable resource classes should inherit from Resource::Base.

There is only one mandatory method to implement to define a resource class. This is the #fabricate! method, which is used to build the resource via the browser UI. Note that you should only use Page objects to interact with a Web page in this method.

Here is an imaginary example: 

module QA
  module Resource
    class Shirt < Base
      attr_accessor :name

      def fabricate!
        Page::Dashboard::Index.perform do |dashboard_index|
          dashboard_index.go_to_new_shirt
        end

        Page::Shirt::New.perform do |shirt_new|
          shirt_new.set_name(name)
          shirt_new.create_shirt!
        end
      end
    end
  end
end

Define API implementation

A resource class may also implement the three following methods to be able to create the resource via the public GitLab API:

  • #api_get_path: The GET path to fetch an existing resource.
  • #api_post_path: The POST path to create a new resource.
  • #api_post_body: The POST body (as a Ruby hash) to create a new resource.

Be aware that many API resources are paginated. If you don’t find the results you expect, check if there is more that one page of results.

Let’s take the Shirt resource class, and add these three API methods: 

module QA
  module Resource
    class Shirt < Base
      attr_accessor :name

      def fabricate!
        # ... same as before
      end

      def api_get_path
        "/shirt/#{name}"
      end

      def api_post_path
        "/shirts"
      end

      def api_post_body
        {
          name: name
        }
      end
    end
  end
end

The Project resource is a good real example of Browser UI and API implementations.

Resource attributes

A resource may need another resource to exist first. For instance, a project needs a group to be created in.

To define a resource attribute, you can use the attribute method with a block using the other resource class to fabricate the resource.

That allows access to the other resource from your resource object’s methods. You would usually use it in #fabricate!, #api_get_path, #api_post_path, #api_post_body.

Let’s take the Shirt resource class, and add a project attribute to it: 

module QA
  module Resource
    class Shirt < Base
      attr_accessor :name

      attribute :project do
        Project.fabricate! do |resource|
          resource.name = 'project-to-create-a-shirt'
        end
      end

      def fabricate!
        project.visit!

        Page::Project::Show.perform do |project_show|
          project_show.go_to_new_shirt
        end

        Page::Shirt::New.perform do |shirt_new|
          shirt_new.set_name(name)
          shirt_new.create_shirt!
        end
      end

      def api_get_path
        "/project/#{project.path}/shirt/#{name}"
      end

      def api_post_path
        "/project/#{project.path}/shirts"
      end

      def api_post_body
        {
          name: name
        }
      end
    end
  end
end

Note that all the attributes are lazily constructed. This means if you want a specific attribute to be fabricated first, you must call the attribute method first even if you’re not using it.

Product data attributes

Once created, you may want to populate a resource with attributes that can be found in the Web page, or in the API response. For instance, once you create a project, you may want to store its repository SSH URL as an attribute.

Again we could use the attribute method with a block, using a page object to retrieve the data on the page.

Let’s take the Shirt resource class, and define a :brand attribute: 

module QA
  module Resource
    class Shirt < Base
      attr_accessor :name

      attribute :project do
        Project.fabricate! do |resource|
          resource.name = 'project-to-create-a-shirt'
        end
      end

      # Attribute populated from the Browser UI (using the block)
      attribute :brand do
        Page::Shirt::Show.perform do |shirt_show|
          shirt_show.fetch_brand_from_page
        end
      end

      # ... same as before
    end
  end
end

Note again that all the attributes are lazily constructed. This means if you call shirt.brand after moving to the other page, it doesn’t properly retrieve the data because we’re no longer on the expected page.

Consider this: 

shirt =
  QA::Resource::Shirt.fabricate! do |resource|
    resource.name = "GitLab QA"
  end

shirt.project.visit!

shirt.brand # => FAIL!

The above example fails because now we’re on the project page, trying to construct the brand data from the shirt page, however we moved to the project page already. There are two ways to solve this, one is that we could try to retrieve the brand before visiting the project again: 

shirt =
  QA::Resource::Shirt.fabricate! do |resource|
    resource.name = "GitLab QA"
  end

shirt.brand # => OK!

shirt.project.visit!

shirt.brand # => OK!

The attribute is stored in the instance, therefore all the following calls are fine, using the data previously constructed. If we think that this might be too brittle, we could eagerly construct the data right before ending fabrication: 

module QA
  module Resource
    class Shirt < Base
      # ... same as before

      def fabricate!
        project.visit!

        Page::Project::Show.perform do |project_show|
          project_show.go_to_new_shirt
        end

        Page::Shirt::New.perform do |shirt_new|
          shirt_new.set_name(name)
          shirt_new.create_shirt!
        end

        populate(:brand) # Eagerly construct the data
      end
    end
  end
end

The populate method iterates through its arguments and call each attribute respectively. Here populate(:brand) has the same effect as just brand. Using the populate method makes the intention clearer.

With this, it ensures we construct the data right after we create the shirt. The drawback is that this always constructs the data when the resource is fabricated even if we don’t need to use the data.

Alternatively, we could just make sure we’re on the right page before constructing the brand data: 

module QA
  module Resource
    class Shirt < Base
      attr_accessor :name

      attribute :project do
        Project.fabricate! do |resource|
          resource.name = 'project-to-create-a-shirt'
        end
      end

      # Attribute populated from the Browser UI (using the block)
      attribute :brand do
        back_url = current_url
        visit!

        Page::Shirt::Show.perform do |shirt_show|
          shirt_show.fetch_brand_from_page
        end

        visit(back_url)
      end

      # ... same as before
    end
  end
end

This ensures it’s on the shirt page before constructing brand, and move back to the previous page to avoid breaking the state.

Define an attribute based on an API response

Sometimes, you want to define a resource attribute based on the API response from its GET or POST request. For instance, if the creation of a shirt via the API returns 

{
  brand: 'a-brand-new-brand',
  style: 't-shirt',
  materials: [[:cotton, 80], [:polyamide, 20]]
}

you may want to store style as-is in the resource, and fetch the first value of the first materials item in a main_fabric attribute.

Let’s take the Shirt resource class, and define a :style and a :main_fabric attributes: 

module QA
  module Resource
    class Shirt < Base
      # ... same as before

      # @style from the instance if present,
      # or fetched from the API response if present,
      # or a QA::Resource::Base::NoValueError is raised otherwise
      attribute :style

      # If @main_fabric is not present,
      # and if the API does not contain this field, this block will be
      # used to construct the value based on the API response, and
      # store the result in @main_fabric
      attribute :main_fabric do
        api_response.&dig(:materials, 0, 0)
      end

      # ... same as before
    end
  end
end

Notes on attributes precedence:

  • resource instance variables have the highest precedence
  • attributes from the API response take precedence over attributes from the block (usually from Browser UI)
  • attributes without a value raises a QA::Resource::Base::NoValueError error

Creating resources in your tests

To create a resource in your tests, you can call the .fabricate! method on the resource class. Note that if the resource class supports API fabrication, this uses this fabrication by default.

Here is an example that uses the API fabrication method under the hood since it’s supported by the Shirt resource class: 

my_shirt = Resource::Shirt.fabricate! do |shirt|
  shirt.name = 'my-shirt'
end

expect(page).to have_text(my_shirt.name) # => "my-shirt" from the resource's instance variable
expect(page).to have_text(my_shirt.brand) # => "a-brand-new-brand" from the API response
expect(page).to have_text(my_shirt.style) # => "t-shirt" from the API response
expect(page).to have_text(my_shirt.main_fabric) # => "cotton" from the API response via the block

If you explicitly want to use the Browser UI fabrication method, you can call the .fabricate_via_browser_ui! method instead: 

my_shirt = Resource::Shirt.fabricate_via_browser_ui! do |shirt|
  shirt.name = 'my-shirt'
end

expect(page).to have_text(my_shirt.name) # => "my-shirt" from the resource's instance variable
expect(page).to have_text(my_shirt.brand) # => the brand name fetched from the `Page::Shirt::Show` page via the block
expect(page).to have_text(my_shirt.style) # => QA::Resource::Base::NoValueError will be raised because no API response nor a block is provided
expect(page).to have_text(my_shirt.main_fabric) # => QA::Resource::Base::NoValueError will be raised because no API response and the block didn't provide a value (because it's also based on the API response)

You can also explicitly use the API fabrication method, by calling the .fabricate_via_api! method: 

my_shirt = Resource::Shirt.fabricate_via_api! do |shirt|
  shirt.name = 'my-shirt'
end

In this case, the result is similar to calling Resource::Shirt.fabricate!.

Reusable resources

Reusable resources are created by the first test that needs a particular kind of resource, and then any test that needs the same kind of resource can reuse it instead of creating a new one.

The ReusableProject resource is an example of this class: 

module QA
  module Resource
    class ReusableProject < Project # A reusable resource inherits from the resource class that we want to be able to reuse.
      prepend Reusable # The Reusable module mixes in some methods that help implement reuse.

      def initialize
        super # A ReusableProject is a Project so it should be initialized as one.

        # Some Project attributes aren't valid and need to be overridden. For example, a ReusableProject keeps its name once it's created,
        # so we don't add a random string to the name specified.
        @add_name_uuid = false

        # It has a default name, and a different name can be specified when a resource is first created. However, the same name must be
        # provided any time that instance of the resource is used.
        @name = "reusable_project"

        # Several instances of a ReusableProject can exists as long as each is identified via a unique value for `reuse_as`.
        @reuse_as = :default_project
      end

      # All reusable resource classes must validate that an instance meets the conditions that allow reuse. For example,
      # by confirming that the name specified for the instance is valid and doesn't conflict with other instances.
      def validate_reuse_preconditions
        raise ResourceReuseError unless reused_name_valid?
      end

      # Internally we identify an instance of a reusable resource by a unique value of `@reuse_as`, but in GitLab the
      # resource has one or more attributes that must also be unique. This method lists those attributes and allows the
      # test framework to check that each instance of a reusable resource has values that match the associated values
      # in Gitlab.
      def unique_identifiers
        [:name, :path]
      end
    end
  end
end

Reusable resources aren’t removed immediately when remove_via_api! is called. Instead, they’re removed after the test suite completes. To do so each class must be registered with QA::Resource::ReusableCollection in qa/spec/spec_helper.rb as in the example below. Registration allows QA::Resource::ReusableCollection to keep track of each instance of each registered class, and to delete them all in the config.after(:suite) hook. 

config.before(:suite) do |suite|
  QA::Resource::ReusableCollection.register_resource_classes do |collection|
    QA::Resource::ReusableProject.register(collection)
  end
end

Consider some examples of how a reusable resource is used: 

# This will create a project.
default_project = Resource::ReusableProject.fabricate_via_api!
default_project.name # => "reusable_project"
default_project.reuse_as # => :default_project

Then in another test we could reuse the project: 

# This will fetch the project created above rather than creating a new one.
default_project_again = Resource::ReusableProject.fabricate_via_api!
default_project_again.name # => "reusable_project"
default_project_again.reuse_as # => :default_project

We can also create another project that we want to change in a way that might not be suitable for tests using the default project: 

project_with_member = Resource::ReusableProject.fabricate_via_api! do |project|
  project.name = "project-with-member"
  project.reuse_as = :project_with_member
end

project_with_member.add_member(user)

Another test can reuse that project: 

project_still_has_member = Resource::ReusableProject.fabricate_via_api! do |project|
  project.name = "project-with-member"
  project.reuse_as = :project_with_member
end

expect(project_still_has_member).to have_member(user)

However, if we don’t provide the name again an error will be raised: 

Resource::ReusableProject.fabricate_via_api! do |project|
  project.reuse_as = :project_with_member
end

# => ResourceReuseError will be raised because it will try to use the default name, "reusable_project", which doesn't
# match the name specified when the project was first fabricated.

Validating reusable resources

Reusable resources can speed up test suites by avoiding the cost of creating the same resource again and again. However, that can cause problems if a test makes changes to a resource that prevent it from being reused as expected by later tests. That can lead to order-dependent test failures that can be difficult to troubleshoot.

For example, the default project created by QA::Resource::ReusableProject has auto_devops_enabled set to false (inherited from QA::Resource::Project). If a test reuses that project and enables Auto DevOps, subsequent tests that reuse the project will fail if they expect Auto DevOps to be disabled.

We try to avoid that kind of trouble by validating reusable resources after a test suite. If the environment variable QA_VALIDATE_RESOURCE_REUSE is set to true the test framework will check each reusable resource to verify that none of the attributes they were created with have been changed. It does that by creating a new resource using the same attributes that were used to create the original resource. It then compares the new resource to the original and raises an error if any attributes don’t match.

Implementation

When you implement a new type of reusable resource there are two private methods you must implement so the resource can be validated. They are:

  • reference_resource: creates a new instance of the resource that can be compared with the one that was used during the tests.
  • unique_identifiers: returns an array of attributes that allow the resource to be identified (e.g., name) and that are therefore expected to differ when comparing the reference resource with the resource reused in the tests.

The following example shows the implementation of those two methods in QA::Resource::ReusableProject. 

# Creates a new project that can be compared to a reused project, using the attributes of the original.
#
# @return [QA::Resource] a new instance of Resource::ReusableProject that should be a copy of the original resource
def reference_resource
  # These are the attributes that the reused resource was created with
  attributes = self.class.resources[reuse_as][:attributes]

  # Two projects can't have the same path, and since we typically use the same value for the name and path, we assign
  # a unique name and path to the reference resource.
  name = "reference_resource_#{SecureRandom.hex(8)}_for_#{attributes.delete(:name)}"

  Project.fabricate_via_api! do |project|
    self.class.resources[reuse_as][:attributes].each do |attribute_name, attribute_value|
      project.instance_variable_set("@#{attribute_name}", attribute_value) if attribute_value
    end
    project.name = name
    project.path = name
    project.path_with_namespace = "#{project.group.full_path}/#{project.name}"
  end
end

# The attributes of the resource that should be the same whenever a test wants to reuse a project.
#
# @return [Array<Symbol>] the attribute names.
def unique_identifiers
  # As noted above, path must be unique, and since we typically use the same value for both, we treat name and path
  # as unique. These attributes are ignored when we compare the reference and reused resources.
  [:name, :path]
end

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.