107 lines
6 KiB
Markdown
107 lines
6 KiB
Markdown
# Flaky tests
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## What's a flaky test?
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It's a test that sometimes fails, but if you retry it enough times, it passes,
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eventually.
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## Quarantined tests
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When a test frequently fails in `master`,
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[a ~"master:broken" issue](https://about.gitlab.com/handbook/engineering/workflow/#broken-master)
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should be created.
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If the test cannot be fixed in a timely fashion, there is an impact on the
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productivity of all the developers, so it should be placed in quarantine by
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assigning the `:quarantine` metadata.
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This means it will be skipped unless run with `--tag quarantine`:
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```shell
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bin/rspec --tag quarantine
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```
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**Before putting a test in quarantine, you should make sure that a
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~"master:broken" issue exists for it so it won't stay in quarantine forever.**
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Once a test is in quarantine, there are 3 choices:
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- Should the test be fixed (i.e. get rid of its flakiness)?
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- Should the test be moved to a lower level of testing?
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- Should the test be removed entirely (e.g. because there's already a
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lower-level test, or it's duplicating another same-level test, or it's testing
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too much etc.)?
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### Quarantine tests on the CI
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Quarantined tests are run on the CI in dedicated jobs that are allowed to fail:
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- `rspec-pg-quarantine` and `rspec-mysql-quarantine` (CE & EE)
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- `rspec-pg-quarantine-ee` and `rspec-mysql-quarantine-ee` (EE only)
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## Automatic retries and flaky tests detection
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On our CI, we use [rspec-retry] to automatically retry a failing example a few
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times (see [`spec/spec_helper.rb`] for the precise retries count).
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We also use a home-made `RspecFlaky::Listener` listener which records flaky
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examples in a JSON report file on `master` (`retrieve-tests-metadata` and `update-tests-metadata` jobs), and warns when a new flaky example
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is detected in any other branch (`flaky-examples-check` job). In the future, the
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`flaky-examples-check` job will not be allowed to fail.
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This was originally implemented in: <https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/13021>.
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[rspec-retry]: https://github.com/NoRedInk/rspec-retry
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[`spec/spec_helper.rb`]: https://gitlab.com/gitlab-org/gitlab-ce/blob/master/spec/spec_helper.rb
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## Problems we had in the past at GitLab
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- [`rspec-retry` is bitting us when some API specs fail](https://gitlab.com/gitlab-org/gitlab-ce/issues/29242): <https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/9825>
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- [Sporadic RSpec failures due to `PG::UniqueViolation`](https://gitlab.com/gitlab-org/gitlab-ce/issues/28307#note_24958837): <https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/9846>
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- Follow-up: <https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/10688>
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- [Capybara.reset_session! should be called before requests are blocked](https://gitlab.com/gitlab-org/gitlab-ce/issues/33779): <https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/12224>
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- FFaker generates funky data that tests are not ready to handle (and tests should be predictable so that's bad!):
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- [Make `spec/mailers/notify_spec.rb` more robust](https://gitlab.com/gitlab-org/gitlab-ce/issues/20121): <https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/10015>
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- [Transient failure in spec/requests/api/commits_spec.rb](https://gitlab.com/gitlab-org/gitlab-ce/issues/27988#note_25342521): <https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/9944>
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- [Replace FFaker factory data with sequences](https://gitlab.com/gitlab-org/gitlab-ce/issues/29643): <https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/10184>
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- [Transient failure in spec/finders/issues_finder_spec.rb](https://gitlab.com/gitlab-org/gitlab-ce/issues/30211#note_26707685): <https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/10404>
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### Time-sensitive flaky tests
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- <https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/10046>
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- <https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/10306>
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### Array order expectation
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- <https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/10148>
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### Feature tests
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- [Be sure to create all the data the test need before starting exercize](https://gitlab.com/gitlab-org/gitlab-ce/issues/32622#note_31128195): <https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/12059>
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- [Bis](https://gitlab.com/gitlab-org/gitlab-ce/issues/34609#note_34048715): <https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/12604>
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- [Bis](https://gitlab.com/gitlab-org/gitlab-ce/issues/34698#note_34276286): <https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/12664>
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- [Assert against the underlying database state instead of against a page's content](https://gitlab.com/gitlab-org/gitlab-ce/issues/31437): <https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/10934>
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#### Capybara viewport size related issues
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- [Transient failure of spec/features/issues/filtered_search/filter_issues_spec.rb](https://gitlab.com/gitlab-org/gitlab-ce/issues/29241#note_26743936): <https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/10411>
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#### Capybara JS driver related issues
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- [Don't wait for AJAX when no AJAX request is fired](https://gitlab.com/gitlab-org/gitlab-ce/issues/30461): <https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/10454>
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- [Bis](https://gitlab.com/gitlab-org/gitlab-ce/issues/34647): <https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/12626>
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#### PhantomJS / WebKit related issues
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- Memory is through the roof! (TL;DR: Load images but block images requests!): <https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/12003>
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## Resources
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- [Flaky Tests: Are You Sure You Want to Rerun Them?](http://semaphoreci.com/blog/2017/04/20/flaky-tests.html)
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- [How to Deal With and Eliminate Flaky Tests](https://semaphoreci.com/community/tutorials/how-to-deal-with-and-eliminate-flaky-tests)
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- [Tips on Treating Flakiness in your Rails Test Suite](http://semaphoreci.com/blog/2017/08/03/tips-on-treating-flakiness-in-your-test-suite.html)
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- ['Flaky' tests: a short story](https://www.ombulabs.com/blog/rspec/continuous-integration/how-to-track-down-a-flaky-test.html)
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- [Using Insights to Discover Flaky, Slow, and Failed Tests](https://circleci.com/blog/using-insights-to-discover-flaky-slow-and-failed-tests/)
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---
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[Return to Testing documentation](index.md)
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