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Contract tests consist of two parts — consumer tests and provider tests. A simple example of a consumer and provider relationship is between the frontend and backend. The frontend would be the consumer and the backend is the provider. The frontend consumes the API that is provided by the backend. The test helps ensure that these two sides follow an agreed upon contract and any divergence from the contract triggers a meaningful conversation to prevent breaking changes from slipping through.
Consumer tests are similar to unit tests with each spec defining a requests and an expected mock responses and creating a contract based on those definitions. On the other hand, provider tests are similar to integration tests as each spec takes the request defined in the contract and runs that request against the actual service which is then matched against the contract to validate the contract.
You can check out the existing contract tests at:
- [`spec/contracts/consumer/specs`](https://gitlab.com/gitlab-org/gitlab/-/tree/master/spec/contracts/consumer/specs) for the consumer tests.
- [`spec/contracts/provider/specs`](https://gitlab.com/gitlab-org/gitlab/-/tree/master/spec/contracts/provider/specs) for the provider tests.
The contracts themselves are stored in [`/spec/contracts/contracts`](https://gitlab.com/gitlab-org/gitlab/-/tree/master/spec/contracts/contracts) at the moment. The plan is to use [PactBroker](https://docs.pact.io/pact_broker/docker_images) hosted in AWS or another similar service.
Before running the consumer tests, go to `spec/contracts/consumer` and run `npm install`. To run all the consumer tests, you just need to run `npm run jest:contract -- /specs`. Otherwise, to run a specific spec file, replace `/specs` with the specific spec filename. Running the consumer test will create the contract that the provider test uses to verify the actual API behavior.
Before running the provider tests, make sure your GDK (GitLab Development Kit) is fully set up and running. You can follow the setup instructions detailed in the [GDK repository](https://gitlab.com/gitlab-org/gitlab-development-kit/-/tree/main). To run the provider tests, you use Rake tasks that can be found in [`./lib/tasks/contracts`](https://gitlab.com/gitlab-org/gitlab/-/tree/master/lib/tasks/contracts). To get a list of all the Rake tasks related to the provider tests, run `bundle exec rake -T contracts`. For example:
By default, the Rake tasks will verify the locally stored contracts. In order to verify the contracts published in the Pact Broker, we need to set the `PACT_BROKER` environment variable to `true` and the `QA_PACT_BROKER_HOST` to the URL of the Pact Broker. It is important to point out here that the file path and file name of the provider test is what is used to find the contract in the Pact Broker which is why it is important to make sure the [provider test naming conventions](#provider-naming) are followed.
The contracts generated by the consumer test can be published to a hosted Pact Broker by setting the `QA_PACT_BROKER_HOST` environment variable and running the [`publish-contracts.sh`](https://gitlab.com/gitlab-org/gitlab/-/tree/master/spec/contracts/publish-contracts.sh) script.
## Test suite folder structure and naming conventions
To keep the consumer and provider test suite organized and maintainable, it's important that tests are organized, also that consumers and providers are named consistently. Therefore, it's important to adhere to the following conventions.
### Test suite folder structure
Having an organized and sensible folder structure for the test suite makes it easier to find relevant files when reviewing, debugging, or introducing tests.
The consumer tests are grouped according to the different pages in the application. Each file contains various types of requests found in a page. As such, the consumer test files are named using the Rails standards of how pages are referenced. For example, the project pipelines page would be the `Project::Pipelines#index` page so the equivalent consumer test would be located in `consumer/specs/project/pipelines/index.spec.js`.
When defining the location to output the contract generated by the test, we want to follow the same file structure which would be `contracts/project/pipelines/` for this example. This is the structure in `consumer/resources` and `consumer/fixtures` as well.
The provider tests are grouped similarly to our controllers. Each of these tests contains various tests for an API endpoint. For example, the API endpoint to get a list of pipelines for a project would be located in `provider/pact_helpers/project/pipelines/get_list_project_pipelines_helper.rb`. The provider states are grouped according to the different pages in the application similar to the consumer tests.
When writing the consumer and provider tests, there are parts where a name is required for the consumer and provider. Since there are no restrictions imposed by Pact on how these should be named, a naming convention is important to keep it easy for us to figure out which consumer and provider tests are involved during debugging. Pact also uses the consumer and provider names to create the locally stored contract file names in the `#{consumer_name}-#{provider_name}` format.
As mentioned in the [folder structure section](#consumer-tests), consumer tests are grouped according to the different pages in the application. As such, consumer names should follow the same naming format using the Rails standard. For example, the consumer test for `Project::Pipelines#index` would be under the `project` folder and will be called `Pipelines#index` as the consumer name.
These are the API endpoints that provides the data to the consumer so they are named according to the API endpoint they pertain to. Be mindful that this begins with the HTTP request method and the rest of the name is as descriptive as possible. For example, if we're writing a test for the `GET /groups/:id/projects` endpoint, we don't want to name it "GET projects endpoint" as there is a `GET /projects` endpoint as well that also fetches a list of projects the user has access to across all of GitLab. To choose an appropriate name, we can start by checking out our [API documentation](../../../api/api_resources.md) and naming it the same way it is named in there while making sure to keep the name in sentence case. So the [`GET /groups/:id/projects`](../../../api/groups.md#list-a-groups-projects) would be called `GET list a group's projects` and [`GET /projects`](../../../api/projects.md#list-all-projects) would be called `GET list all projects`. Subsequently, the test files are named `get_list_a_groups_projects_helper.rb` and `get_list_all_projects_helper.rb` respectively.
There are some cases where the provider being tested may not be documented so, in those cases, fall back to starting with the HTTP request method followed by a name that is as descriptive as possible to ensure it's easy to tell what the provider is for.
| Consumer Test | Follows the Rails reference standards. For example, `Project::Pipelines#index` would be `consumer/specs/project/pipelines/index.spec.js` | Follows the Rails naming standard. For example, `Project::Pipelines#index` would be `Pipelines#index` within the `project` folder. |
| Provider Test | Grouped like the Rails controllers. For example, [`GET list project pipelines` API endpoint](../../../api/pipelines.md#list-project-pipelines) would be `provider/pact_helpers/project/pipelines/provider/pact_helpers/project/pipelines/get_list_project_pipelines_helper.rb` | Follows the API documentation naming scheme in sentence case. For example, [`GET /projects/:id/pipelines`](../../../api/pipelines.md#list-project-pipelines) would be called `GET list project pipelines`. |
