98 lines
3.9 KiB
Markdown
98 lines
3.9 KiB
Markdown
---
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stage: Verify
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group: Testing
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info: To determine the technical writer assigned to the Stage/Group associated with this page, see https://about.gitlab.com/handbook/engineering/ux/technical-writing/#assignments
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type: reference, howto
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---
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# Fail Fast Testing **(PREMIUM)**
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> [Introduced](https://gitlab.com/gitlab-org/gitlab/-/issues/198550) in GitLab 13.1.
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For applications that use RSpec for running tests, we've introduced the `Verify/Failfast`
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[template to run subsets of your test suite](https://gitlab.com/gitlab-org/gitlab/-/tree/master/lib/gitlab/ci/templates/Verify/FailFast.gitlab-ci.yml),
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based on the changes in your merge request.
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The template uses the [test_file_finder (`tff`) gem](https://gitlab.com/gitlab-org/ci-cd/test_file_finder/)
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that accepts a list of files as input, and returns a list of spec (test) files
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that it believes to be relevant to the input files.
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`tff` is designed for Ruby on Rails projects, so the `Verify/FailFast` template is
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configured to run when changes to Ruby files are detected. By default, it runs in
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the [`.pre` stage](../../../ci/yaml/index.md#pre-and-post) of a GitLab CI/CD pipeline,
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before all other stages.
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## Example use case
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Fail fast testing is useful when adding new functionality to a project and adding
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new automated tests.
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Your project could have hundreds of thousands of tests that take a long time to complete.
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You may be confident that a new test will pass, but you have to wait for all the tests
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to complete to verify it. This could take an hour or more, even when using parallelization.
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Fail fast testing gives you a faster feedback loop from the pipeline. It lets you
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know quickly that the new tests are passing and the new functionality did not break
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other tests.
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## Requirements
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This template requires:
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- A project built in Rails that uses RSpec for testing.
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- CI/CD configured to:
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- Use a Docker image with Ruby available.
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- Use [Pipelines for merge requests](../../../ci/pipelines/merge_request_pipelines.md#configure-pipelines-for-merge-requests)
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- [Pipelines for Merged Results](../../../ci/pipelines/pipelines_for_merged_results.md#enable-pipelines-for-merged-results)
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enabled in the project settings.
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- A Docker image with Ruby available. The template uses `image: ruby:2.6` by default, but you [can override](../../../ci/yaml/includes.md#overriding-external-template-values) this.
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## Configuring Fast RSpec Failure
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We use the following plain RSpec configuration as a starting point. It installs all the
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project gems and executes `rspec`, on merge request pipelines only.
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```yaml
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rspec-complete:
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stage: test
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rules:
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- if: $CI_PIPELINE_SOURCE == "merge_request_event"
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script:
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- bundle install
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- bundle exec rspec
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```
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To run the most relevant specs first instead of the whole suite, [`include`](../../../ci/yaml/index.md#include)
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the template by adding the following to your CI/CD configuration:
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```yaml
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include:
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- template: Verify/FailFast.gitlab-ci.yml
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```
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To customize the job, specific options may be set to override the template. For example, to override the default Docker image:
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```yaml
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include:
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- template: Verify/FailFast.gitlab-ci.yml
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rspec-rails-modified-path-specs:
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image: custom-docker-image-with-ruby
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```
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### Example test loads
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For illustrative purposes, let's say our Rails app spec suite consists of 100 specs per model for ten models.
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If no Ruby files are changed:
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- `rspec-rails-modified-paths-specs` does not run any tests.
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- `rspec-complete` runs the full suite of 1000 tests.
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If one Ruby model is changed, for example `app/models/example.rb`, then `rspec-rails-modified-paths-specs`
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runs the 100 tests for `example.rb`:
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- If all of these 100 tests pass, then the full `rspec-complete` suite of 1000 tests is allowed to run.
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- If any of these 100 tests fail, they fail quickly, and `rspec-complete` does not run any tests.
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The final case saves resources and time as the full 1000 test suite does not run.
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