[EE] Refactor the testing documentation and divide it into multiple pages

Signed-off-by: Rémy Coutable <remy@rymai.me>

CONTRIBUTING.md

@@ -297,9 +297,9 @@ might be edited to make them small and simple.
 
 Please submit Feature Proposals using the ['Feature Proposal' issue template](.gitlab/issue_templates/Feature Proposal.md) provided on the issue tracker.
 
-For changes in the interface, it is helpful to include a mockup. Issues that add to, or change, the interface should 
-be given the ~"UX" label. This will allow the UX team to provide input and guidance. You may 
-need to ask one of the [core team] members to add the label, if you do not have permissions to do it by yourself. 
+For changes in the interface, it is helpful to include a mockup. Issues that add to, or change, the interface should
+be given the ~"UX" label. This will allow the UX team to provide input and guidance. You may
+need to ask one of the [core team] members to add the label, if you do not have permissions to do it by yourself.
 
 If you want to create something yourself, consider opening an issue first to
 discuss whether it is interesting to include this in GitLab.
@@ -677,7 +677,7 @@ When your code contains more than 500 changes, any major breaking changes, or an
 [license-finder-doc]: doc/development/licensing.md
 [GitLab Inc engineering workflow]: https://about.gitlab.com/handbook/engineering/workflow/#labelling-issues
 [polling-etag]: https://docs.gitlab.com/ce/development/polling.html
-[testing]: doc/development/testing.md
+[testing]: doc/development/testing_guide/index.md
 
 [^1]: Please note that specs other than JavaScript specs are considered backend
       code.

PROCESS.md

-## GitLab Core Team & GitLab Inc. Contribution Process
+## GitLab core team & GitLab Inc. contribution process
 
 ---
 

doc/development/README.md

-# Development
+# GitLab development guides
 
-## Outside of docs
+## Get started!
 
-- [CONTRIBUTING.md](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md) main contributing guide
-- [PROCESS.md](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/PROCESS.md) contributing process
-- [GitLab Development Kit (GDK)](https://gitlab.com/gitlab-org/gitlab-development-kit/blob/master/doc/howto/README.md) to install a development version
-
-## Styleguides
-
-- [API styleguide](api_styleguide.md) Use this styleguide if you are
-  contributing to the API.
-- [Documentation styleguide](doc_styleguide.md) Use this styleguide if you are
-  contributing to documentation.
-- [Writing documentation](writing_documentation.md)
-  - [Distinction between general documentation and technical articles](writing_documentation.md#distinction-between-general-documentation-and-technical-articles)
-- [SQL Migration Style Guide](migration_style_guide.md) for creating safe SQL migrations
-- [Testing standards and style guidelines](testing.md)
-- [UX guide](ux_guide/index.md) for building GitLab with existing CSS styles and elements
-- [Frontend guidelines](fe_guide/index.md)
-- [SQL guidelines](sql.md) for working with SQL queries
-- [Sidekiq guidelines](sidekiq_style_guide.md) for working with Sidekiq workers
-- [`Gemfile` guidelines](gemfile.md)
+- Setup GitLab's development environment with [GitLab Development Kit (GDK)](https://gitlab.com/gitlab-org/gitlab-development-kit/blob/master/doc/howto/README.md)
+- [GitLab contributing guide](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md)
+- [Architecture](architecture.md) of GitLab
+- [Rake tasks](rake_tasks.md) for development
 
-## Process
+## Processes
 
+- [GitLab core team & GitLab Inc. contribution process](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/PROCESS.md)
 - [Generate a changelog entry with `bin/changelog`](changelog.md)
+- [Code review guidelines](code_review.md) for reviewing code and having code reviewed.
 - [Limit conflicts with EE when developing on CE](limit_ee_conflicts.md)
 - [Guidelines for implementing Enterprise Edition feature](ee_features.md)
-- [Code review guidelines](code_review.md) for reviewing code and having code reviewed.
-- [Merge request performance guidelines](merge_request_performance_guidelines.md)
-  for ensuring merge requests do not negatively impact GitLab performance
 
-## Backend howtos
+## UX and frontend guides
 
-- [Architecture](architecture.md) of GitLab
+- [UX guide](ux_guide/index.md) for building GitLab with existing CSS styles and elements
+- [Frontend guidelines](fe_guide/index.md)
+
+## Backend guides
+
+- [Testing standards and style guidelines](testing_guide/index.md)
+- [API styleguide](api_styleguide.md) Use this styleguide if you are
+  contributing to the API.
+- [Sidekiq guidelines](sidekiq_style_guide.md) for working with Sidekiq workers
+- [Working with Gitaly](gitaly.md)
+- [Manage feature flags](feature_flags.md)
+- [View sent emails or preview mailers](emails.md)
+- [Shell commands](shell_commands.md) in the GitLab codebase
+- [`Gemfile` guidelines](gemfile.md)
+- [Sidekiq debugging](sidekiq_debugging.md)
 - [Gotchas](gotchas.md) to avoid
+- [Issue and merge requests state models](object_state_models.md)
 - [How to dump production data to staging](db_dump.md)
+
+## Performance guides
+
 - [Instrumentation](instrumentation.md)
 - [Performance guidelines](performance.md)
-- [Rake tasks](rake_tasks.md) for development
-- [Shell commands](shell_commands.md) in the GitLab codebase
-- [Sidekiq debugging](sidekiq_debugging.md)
-- [Object state models](object_state_models.md)
-- [Building a package for testing purposes](build_test_package.md)
-- [Manage feature flags](feature_flags.md)
-- [View sent emails or preview mailers](emails.md)
-- [Working with Gitaly](gitaly.md)
+- [Merge request performance guidelines](merge_request_performance_guidelines.md)
+  for ensuring merge requests do not negatively impact GitLab performance
+
+## Databases guides
 
-## Databases
+### Migrations
 
-- [Merge Request Checklist](database_merge_request_checklist.md)
 - [What requires downtime?](what_requires_downtime.md)
+- [SQL guidelines](sql.md) for working with SQL queries
+- [Migrations style guide](migration_style_guide.md) for creating safe SQL migrations
+- [Post deployment migrations](post_deployment_migrations.md)
+- [Background migrations](background_migrations.md)
+- [Swapping tables](swapping_tables.md)
+
+### Best practices
+
+- [Merge Request checklist](database_merge_request_checklist.md)
 - [Adding database indexes](adding_database_indexes.md)
-- [Post Deployment Migrations](post_deployment_migrations.md)
-- [Foreign Keys & Associations](foreign_keys.md)
-- [Serializing Data](serializing_data.md)
-- [Polymorphic Associations](polymorphic_associations.md)
-- [Single Table Inheritance](single_table_inheritance.md)
-- [Background Migrations](background_migrations.md)
-- [Storing SHA1 Hashes As Binary](sha1_as_binary.md)
-- [Iterating Tables In Batches](iterating_tables_in_batches.md)
-- [Ordering Table Columns](ordering_table_columns.md)
-- [Verifying Database Capabilities](verifying_database_capabilities.md)
-- [Hash Indexes](hash_indexes.md)
-- [Swapping Tables](swapping_tables.md)
-
-## Internationalization (i18n)
+- [Foreign keys & associations](foreign_keys.md)
+- [Single table inheritance](single_table_inheritance.md)
+- [Polymorphic associations](polymorphic_associations.md)
+- [Serializing data](serializing_data.md)
+- [Hash indexes](hash_indexes.md)
+- [Storing SHA1 hashes as binary](sha1_as_binary.md)
+- [Iterating tables in batches](iterating_tables_in_batches.md)
+- [Ordering table columns](ordering_table_columns.md)
+- [Verifying database capabilities](verifying_database_capabilities.md)
+
+## Documentation guides
+
+- [Documentation styleguide](doc_styleguide.md): Use this styleguide if you are
+  contributing to the documentation.
+- [Writing documentation](writing_documentation.md)
+  - [Distinction between general documentation and technical articles](writing_documentation.md#distinction-between-general-documentation-and-technical-articles)
+
+## Internationalization (i18n) guides
 
 - [Introduction](i18n/index.md)
 - [Externalization](i18n/externalization.md)
 - [Translation](i18n/translation.md)
 
+## Build guides
+
+- [Building a package for testing purposes](build_test_package.md)
+
 ## Compliance
 
 - [Licensing](licensing.md) for ensuring license compliance

doc/development/fe_guide/index.md

@@ -54,7 +54,8 @@ or make changes to our frontend development guidelines.
 
 ---
 
-## [Testing](testing.md)
+## [Testing](../testing_guide/frontend_testing.md)
+
 How we write frontend tests, run the GitLab test suite, and debug test related
 issues.
 

doc/development/fe_guide/testing.md

-# Frontend Testing
-
-There are two types of test suites you'll encounter while developing frontend code
-at GitLab.  We use Karma and Jasmine for JavaScript unit and integration testing, and RSpec
-feature tests with Capybara for e2e (end-to-end) integration testing.
-
-Unit and feature tests need to be written for all new features.
-Most of the time, you should use rspec for your feature tests.
-There are cases where the behaviour you are testing is not worth the time spent running the full application,
-for example, if you are testing styling, animation, edge cases or small actions that don't involve the backend,
-you should write an integration test using Jasmine.
-
-![Testing priority triangle](img/testing_triangle.png)
-
-_This diagram demonstrates the relative priority of each test type we use_
-
-Regression tests should be written for bug fixes to prevent them from recurring in the future.
-
-See [the Testing Standards and Style Guidelines](../testing.md)
-for more information on general testing practices at GitLab.
-
-## Karma test suite
-
-GitLab uses the [Karma][karma] test runner with [Jasmine][jasmine] as its test
-framework for our JavaScript unit and integration tests. For integration tests,
-we generate HTML files using RSpec (see `spec/javascripts/fixtures/*.rb` for examples).
-Some fixtures are still HAML templates that are translated to HTML files using the same mechanism (see `static_fixtures.rb`).
-Adding these static fixtures should be avoided as they are harder to keep up to date with real views.
-The existing static fixtures will be migrated over time.
-Please see [gitlab-org/gitlab-ce#24753](https://gitlab.com/gitlab-org/gitlab-ce/issues/24753) to track our progress.
-Fixtures are served during testing by the [jasmine-jquery][jasmine-jquery] plugin.
-
-JavaScript tests live in `spec/javascripts/`, matching the folder structure
-of `app/assets/javascripts/`: `app/assets/javascripts/behaviors/autosize.js`
-has a corresponding `spec/javascripts/behaviors/autosize_spec.js` file.
-
-Keep in mind that in a CI environment, these tests are run in a headless
-browser and you will not have access to certain APIs, such as
-[`Notification`](https://developer.mozilla.org/en-US/docs/Web/API/notification),
-which will have to be stubbed.
-
-### Best practice
-
-#### Naming unit tests
-
-When writing describe test blocks to test specific functions/methods,
-please use the method name as the describe block name.
-
-```javascript
-// Good
-describe('methodName', () => {
-  it('passes', () => {
-    expect(true).toEqual(true);
-  });
-});
-
-// Bad
-describe('#methodName', () => {
-  it('passes', () => {
-    expect(true).toEqual(true);
-  });
-});
-
-// Bad
-describe('.methodName', () => {
-  it('passes', () => {
-    expect(true).toEqual(true);
-  });
-});
-```
-#### Testing Promises
-
-When testing Promises you should always make sure that the test is asynchronous and rejections are handled.
-Your Promise chain should therefore end with a call of the `done` callback and `done.fail` in case an error occurred.
-
-```javascript
-// Good
-it('tests a promise', (done) => {
-  promise
-    .then((data) => {
-      expect(data).toBe(asExpected);
-    })
-    .then(done)
-    .catch(done.fail);
-});
-
-// Good
-it('tests a promise rejection', (done) => {
-  promise
-    .then(done.fail)
-    .catch((error) => {
-      expect(error).toBe(expectedError);
-    })
-    .then(done)
-    .catch(done.fail);
-});
-
-// Bad (missing done callback)
-it('tests a promise', () => {
-  promise
-    .then((data) => {
-      expect(data).toBe(asExpected);
-    })
-});
-
-// Bad (missing catch)
-it('tests a promise', (done) => {
-  promise
-    .then((data) => {
-      expect(data).toBe(asExpected);
-    })
-    .then(done)
-});
-
-// Bad (use done.fail in asynchronous tests)
-it('tests a promise', (done) => {
-  promise
-    .then((data) => {
-      expect(data).toBe(asExpected);
-    })
-    .then(done)
-    .catch(fail)
-});
-
-// Bad (missing catch)
-it('tests a promise rejection', (done) => {
-  promise
-    .catch((error) => {
-      expect(error).toBe(expectedError);
-    })
-    .then(done)
-});
-```
-
-#### Stubbing
-
-For unit tests, you should stub methods that are unrelated to the current unit you are testing.
-If you need to use a prototype method, instantiate an instance of the class and call it there instead of mocking the instance completely.
-
-For integration tests, you should stub methods that will effect the stability of the test if they
-execute their original behaviour. i.e. Network requests.
-
-### Vue.js unit tests
-See this [section][vue-test].
-
-### Running frontend tests
-
-`rake karma` runs the frontend-only (JavaScript) tests.
-It consists of two subtasks:
-
-- `rake karma:fixtures` (re-)generates fixtures
-- `rake karma:tests` actually executes the tests
-
-As long as the fixtures don't change, `rake karma:tests` (or `yarn karma`)
-is sufficient (and saves you some time).
-
-### Live testing and focused testing
-
-While developing locally, it may be helpful to keep karma running so that you
-can get instant feedback on as you write tests and modify code.  To do this
-you can start karma with `npm run karma-start`.  It will compile the javascript
-assets and run a server at `http://localhost:9876/` where it will automatically
-run the tests on any browser which connects to it.  You can enter that url on
-multiple browsers at once to have it run the tests on each in parallel.
-
-While karma is running, any changes you make will instantly trigger a recompile
-and retest of the entire test suite, so you can see instantly if you've broken
-a test with your changes.  You can use [jasmine focused][jasmine-focus] or
-excluded tests (with `fdescribe` or `xdescribe`) to get karma to run only the
-tests you want while you're working on a specific feature, but make sure to
-remove these directives when you commit your code.
-
-## RSpec Feature Integration Tests
-
-Information on setting up and running RSpec integration tests with
-[Capybara][capybara] can be found in the
-[general testing guide](../testing.md).
-
-## Gotchas
-
-### Errors due to use of unsupported JavaScript features
-
-Similar errors will be thrown if you're using JavaScript features not yet
-supported by the PhantomJS test runner which is used for both Karma and RSpec
-tests.  We polyfill some JavaScript objects for older browsers, but some
-features are still unavailable:
-
-- Array.from
-- Array.first
-- Async functions
-- Generators
-- Array destructuring
-- For..Of
-- Symbol/Symbol.iterator
-- Spread
-
-Until these are polyfilled appropriately, they should not be used.  Please
-update this list with additional unsupported features.
-
-### RSpec errors due to JavaScript
-
-By default RSpec unit tests will not run JavaScript in the headless browser
-and will simply rely on inspecting the HTML generated by rails.
-
-If an integration test depends on JavaScript to run correctly, you need to make
-sure the spec is configured to enable JavaScript when the tests are run. If you
-don't do this you'll see vague error messages from the spec runner.
-
-To enable a JavaScript driver in an `rspec` test, add `:js` to the
-individual spec or the context block containing multiple specs that need
-JavaScript enabled:
-
-```ruby
-# For one spec
-it 'presents information about abuse report', :js do
-  # assertions...
-end
-
-describe "Admin::AbuseReports", :js do
-  it 'presents information about abuse report' do
-    # assertions...
-  end
-  it 'shows buttons for adding to abuse report' do
-    # assertions...
-  end
-end
-```
-
-### Spinach errors due to missing JavaScript
-
-> **Note:** Since we are discouraging the use of Spinach when writing new
-> feature tests, you shouldn't ever need to use this.  This information is kept
-> available for legacy purposes only.
-
-In Spinach, the JavaScript driver is enabled differently. In the `*.feature`
-file for the failing spec, add the `@javascript` flag above the Scenario:
-
-```
-@javascript
-Scenario: Developer can approve merge request
-  Given I am a "Shop" developer
-  And I visit project "Shop" merge requests page
-  And merge request 'Bug NS-04' must be approved
-  And I click link "Bug NS-04"
-  When I click link "Approve"
-  Then I should see approved merge request "Bug NS-04"
-```
-
-[capybara]: http://teamcapybara.github.io/capybara/
-[jasmine]: https://jasmine.github.io/
-[jasmine-focus]: https://jasmine.github.io/2.5/focused_specs.html
-[jasmine-jquery]: https://github.com/velesin/jasmine-jquery
-[karma]: http://karma-runner.github.io/
-[vue-test]:https://docs.gitlab.com/ce/development/fe_guide/vue.html#testing-vue-components
+This document was moved to [../testing_guide/frontend_testing.md](../testing_guide/frontend_testing.md).

doc/development/testing_guide/ci.md

+# GitLab tests in the Continuous Integration (CI) context
+
+### Test suite parallelization on the CI
+
+Our current CI parallelization setup is as follows:
+
+1. The `knapsack` job in the prepare stage that is supposed to ensure we have a
+  `knapsack/${CI_PROJECT_NAME}/rspec_report-master.json` file:
+  - The `knapsack/${CI_PROJECT_NAME}/rspec_report-master.json` file is fetched
+    from S3, if it's not here we initialize the file with `{}`.
+1. Each `rspec x y` job are run with `knapsack rspec` and should have an evenly
+  distributed share of tests:
+  - It works because the jobs have access to the
+    `knapsack/${CI_PROJECT_NAME}/rspec_report-master.json` since the "artifacts
+    from all previous stages are passed by default". [^1]
+  - the jobs set their own report path to
+    `KNAPSACK_REPORT_PATH=knapsack/${CI_PROJECT_NAME}/${JOB_NAME[0]}_node_${CI_NODE_INDEX}_${CI_NODE_TOTAL}_report.json`.
+  - if knapsack is doing its job, test files that are run should be listed under
+    `Report specs`, not under `Leftover specs`.
+1. The `update-knapsack` job takes all the
+  `knapsack/${CI_PROJECT_NAME}/${JOB_NAME[0]}_node_${CI_NODE_INDEX}_${CI_NODE_TOTAL}_report.json`
+  files from the `rspec x y` jobs and merge them all together into a single
+  `knapsack/${CI_PROJECT_NAME}/rspec_report-master.json` file that is then
+  uploaded to S3.
+
+After that, the next pipeline will use the up-to-date
+`knapsack/${CI_PROJECT_NAME}/rspec_report-master.json` file. The same strategy
+is used for Spinach tests as well.
+
+### Monitoring
+
+The GitLab test suite is [monitored] for the `master` branch, and any branch
+that includes `rspec-profile` in their name.
+
+A [public dashboard] is available for everyone to see. Feel free to look at the
+slowest test files and try to improve them.
+
+[monitored]: ../performance.md#rspec-profiling
+[public dashboard]: https://redash.gitlab.com/public/dashboards/l1WhHXaxrCWM5Ai9D7YDqHKehq6OU3bx5gssaiWe?org_slug=default
+
+## CI setup
+
+- On CE and EE, the test suite runs both PostgreSQL and MySQL.
+- Rails logging to `log/test.log` is disabled by default in CI [for
+  performance reasons][logging]. To override this setting, provide the
+  `RAILS_ENABLE_TEST_LOG` environment variable.
+
+[logging]: https://jtway.co/speed-up-your-rails-test-suite-by-6-in-1-line-13fedb869ec4
+
+---
+
+[Return to Testing documentation](index.md)

doc/development/testing_guide/flaky_tests.md

+# Flaky tests
+
+## What's a flaky test?
+
+It's a test that sometimes fails, but if you retry it enough times, it passes,
+eventually.
+
+## Automatic retries and flaky tests detection
+
+On our CI, we use [rspec-retry] to automatically retry a failing example a few
+times (see [`spec/spec_helper.rb`] for the precise retries count).
+
+We also use a home-made `RspecFlaky::Listener` listener which records flaky
+examples in a JSON report file on `master` (`retrieve-tests-metadata` and `update-tests-metadata` jobs), and warns when a new flaky example
+is detected in any other branch (`flaky-examples-check` job). In the future, the
+`flaky-examples-check` job will not be allowed to fail.
+
+This was originally implemented in: https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/13021.
+
+[rspec-retry]: https://github.com/NoRedInk/rspec-retry
+[`spec/spec_helper.rb`]: https://gitlab.com/gitlab-org/gitlab-ce/blob/master/spec/spec_helper.rb
+
+## Problems we had in the past at GitLab
+
+- [`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
+- [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
+  - Follow-up: https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/10688
+  - [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
+- FFaker generates funky data that tests are not ready to handle (and tests should be predictable so that's bad!):
+  - [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
+  - [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
+  - [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
+  - [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
+
+### Time-sensitive flaky tests
+
+- https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/10046
+- https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/10306
+
+### Array order expectation
+
+- https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/10148
+
+### Feature tests
+
+- [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
+- [Bis](https://gitlab.com/gitlab-org/gitlab-ce/issues/34609#note_34048715): https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/12604
+- [Bis](https://gitlab.com/gitlab-org/gitlab-ce/issues/34698#note_34276286): https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/12664
+- [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
+
+#### Capybara viewport size related issues
+
+- [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
+
+#### Capybara JS driver related issues
+
+- [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
+- [Bis](https://gitlab.com/gitlab-org/gitlab-ce/issues/34647): https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/12626
+
+#### PhantomJS / WebKit related issues
+
+- Memory is through the roof! (TL;DR: Load images but block images requests!): https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/12003
+
+## Resources
+
+- [Flaky Tests: Are You Sure You Want to Rerun Them?](http://semaphoreci.com/blog/2017/04/20/flaky-tests.html)
+- [How to Deal With and Eliminate Flaky Tests](https://semaphoreci.com/community/tutorials/how-to-deal-with-and-eliminate-flaky-tests)
+- [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)
+- ['Flaky' tests: a short story](https://www.ombulabs.com/blog/rspec/continuous-integration/how-to-track-down-a-flaky-test.html)
+- [Using Insights to Discover Flaky, Slow, and Failed Tests](https://circleci.com/blog/using-insights-to-discover-flaky-slow-and-failed-tests/)
+
+---
+
+[Return to Testing documentation](index.md)

doc/development/testing_guide/frontend_testing.md

+# Frontend testing standards and style guidelines
+
+There are two types of test suites you'll encounter while developing frontend code
+at GitLab. We use Karma and Jasmine for JavaScript unit and integration testing,
+and RSpec feature tests with Capybara for e2e (end-to-end) integration testing.
+
+Unit and feature tests need to be written for all new features.
+Most of the time, you should use [RSpec] for your feature tests.
+
+Regression tests should be written for bug fixes to prevent them from recurring
+in the future.
+
+See the [Testing Standards and Style Guidelines](index.md) page for more
+information on general testing practices at GitLab.
+
+## Karma test suite
+
+GitLab uses the [Karma][karma] test runner with [Jasmine] as its test
+framework for our JavaScript unit and integration tests. For integration tests,
+we generate HTML files using RSpec (see `spec/javascripts/fixtures/*.rb` for examples).
+Some fixtures are still HAML templates that are translated to HTML files using the same mechanism (see `static_fixtures.rb`).
+Adding these static fixtures should be avoided as they are harder to keep up to date with real views.
+The existing static fixtures will be migrated over time.
+Please see [gitlab-org/gitlab-ce#24753](https://gitlab.com/gitlab-org/gitlab-ce/issues/24753) to track our progress.
+Fixtures are served during testing by the [jasmine-jquery][jasmine-jquery] plugin.
+
+JavaScript tests live in `spec/javascripts/`, matching the folder structure
+of `app/assets/javascripts/`: `app/assets/javascripts/behaviors/autosize.js`
+has a corresponding `spec/javascripts/behaviors/autosize_spec.js` file.
+
+Keep in mind that in a CI environment, these tests are run in a headless
+browser and you will not have access to certain APIs, such as
+[`Notification`](https://developer.mozilla.org/en-US/docs/Web/API/notification),
+which will have to be stubbed.
+
+### Best practices
+
+#### Naming unit tests
+
+When writing describe test blocks to test specific functions/methods,
+please use the method name as the describe block name.
+
+```javascript
+// Good
+describe('methodName', () => {
+  it('passes', () => {
+    expect(true).toEqual(true);
+  });
+});
+
+// Bad
+describe('#methodName', () => {
+  it('passes', () => {
+    expect(true).toEqual(true);
+  });
+});
+
+// Bad
+describe('.methodName', () => {
+  it('passes', () => {
+    expect(true).toEqual(true);
+  });
+});
+```
+#### Testing promises
+
+When testing Promises you should always make sure that the test is asynchronous and rejections are handled.
+Your Promise chain should therefore end with a call of the `done` callback and `done.fail` in case an error occurred.
+
+```javascript
+// Good
+it('tests a promise', (done) => {
+  promise
+    .then((data) => {
+      expect(data).toBe(asExpected);
+    })
+    .then(done)
+    .catch(done.fail);
+});
+
+// Good
+it('tests a promise rejection', (done) => {
+  promise
+    .then(done.fail)
+    .catch((error) => {
+      expect(error).toBe(expectedError);
+    })
+    .then(done)
+    .catch(done.fail);
+});
+
+// Bad (missing done callback)
+it('tests a promise', () => {
+  promise
+    .then((data) => {
+      expect(data).toBe(asExpected);
+    })
+});
+
+// Bad (missing catch)
+it('tests a promise', (done) => {
+  promise
+    .then((data) => {
+      expect(data).toBe(asExpected);
+    })
+    .then(done)
+});
+
+// Bad (use done.fail in asynchronous tests)
+it('tests a promise', (done) => {
+  promise
+    .then((data) => {
+      expect(data).toBe(asExpected);
+    })
+    .then(done)
+    .catch(fail)
+});
+
+// Bad (missing catch)
+it('tests a promise rejection', (done) => {
+  promise
+    .catch((error) => {
+      expect(error).toBe(expectedError);
+    })
+    .then(done)
+});
+```
+
+#### Stubbing
+
+For unit tests, you should stub methods that are unrelated to the current unit you are testing.
+If you need to use a prototype method, instantiate an instance of the class and call it there instead of mocking the instance completely.
+
+For integration tests, you should stub methods that will effect the stability of the test if they
+execute their original behaviour. i.e. Network requests.
+
+### Vue.js unit tests
+
+See this [section][vue-test].
+
+### Running frontend tests
+
+`rake karma` runs the frontend-only (JavaScript) tests.
+It consists of two subtasks:
+
+- `rake karma:fixtures` (re-)generates fixtures
+- `rake karma:tests` actually executes the tests
+
+As long as the fixtures don't change, `rake karma:tests` (or `yarn karma`)
+is sufficient (and saves you some time).
+
+### Live testing and focused testing
+
+While developing locally, it may be helpful to keep karma running so that you
+can get instant feedback on as you write tests and modify code.  To do this
+you can start karma with `npm run karma-start`.  It will compile the javascript
+assets and run a server at `http://localhost:9876/` where it will automatically
+run the tests on any browser which connects to it.  You can enter that url on
+multiple browsers at once to have it run the tests on each in parallel.
+
+While karma is running, any changes you make will instantly trigger a recompile
+and retest of the entire test suite, so you can see instantly if you've broken
+a test with your changes.  You can use [jasmine focused][jasmine-focus] or
+excluded tests (with `fdescribe` or `xdescribe`) to get karma to run only the
+tests you want while you're working on a specific feature, but make sure to
+remove these directives when you commit your code.
+
+## RSpec feature integration tests
+
+Information on setting up and running RSpec integration tests with
+[Capybara] can be found in the [Testing Best Practices](best_practices.md).
+
+## Gotchas
+
+### Errors due to use of unsupported JavaScript features
+
+Similar errors will be thrown if you're using JavaScript features not yet
+supported by the PhantomJS test runner which is used for both Karma and RSpec
+tests.  We polyfill some JavaScript objects for older browsers, but some
+features are still unavailable:
+
+- Array.from
+- Array.first
+- Async functions
+- Generators
+- Array destructuring
+- For..Of
+- Symbol/Symbol.iterator
+- Spread
+
+Until these are polyfilled appropriately, they should not be used.  Please
+update this list with additional unsupported features.
+
+### RSpec errors due to JavaScript
+
+By default RSpec unit tests will not run JavaScript in the headless browser
+and will simply rely on inspecting the HTML generated by rails.
+
+If an integration test depends on JavaScript to run correctly, you need to make
+sure the spec is configured to enable JavaScript when the tests are run. If you
+don't do this you'll see vague error messages from the spec runner.
+
+To enable a JavaScript driver in an `rspec` test, add `:js` to the
+individual spec or the context block containing multiple specs that need
+JavaScript enabled:
+
+```ruby
+# For one spec
+it 'presents information about abuse report', :js do
+  # assertions...
+end
+
+describe "Admin::AbuseReports", :js do
+  it 'presents information about abuse report' do
+    # assertions...
+  end
+  it 'shows buttons for adding to abuse report' do
+    # assertions...
+  end
+end
+```
+
+### Spinach errors due to missing JavaScript
+
+NOTE: **Note:** Since we are discouraging the use of Spinach when writing new
+feature tests, you shouldn't ever need to use this.  This information is kept
+available for legacy purposes only.
+
+In Spinach, the JavaScript driver is enabled differently. In the `*.feature`
+file for the failing spec, add the `@javascript` flag above the Scenario:
+
+```
+@javascript
+Scenario: Developer can approve merge request
+  Given I am a "Shop" developer
+  And I visit project "Shop" merge requests page
+  And merge request 'Bug NS-04' must be approved
+  And I click link "Bug NS-04"
+  When I click link "Approve"
+  Then I should see approved merge request "Bug NS-04"
+```
+
+[jasmine-focus]: https://jasmine.github.io/2.5/focused_specs.html
+[jasmine-jquery]: https://github.com/velesin/jasmine-jquery
+[karma]: http://karma-runner.github.io/
+[vue-test]:https://docs.gitlab.com/ce/development/fe_guide/vue.html#testing-vue-components
+[RSpec]: https://github.com/rspec/rspec-rails#feature-specs
+[Capybara]: https://github.com/teamcapybara/capybara
+[Karma]: http://karma-runner.github.io/
+[Jasmine]: https://jasmine.github.io/
+
+---
+
+[Return to Testing documentation](index.md)

doc/development/testing_guide/index.md

+# Testing standards and style guidelines
+
+This document describes various guidelines and best practices for automated
+testing of the GitLab project.
+
+It is meant to be an _extension_ of the [thoughtbot testing
+styleguide](https://github.com/thoughtbot/guides/tree/master/style/testing). If
+this guide defines a rule that contradicts the thoughtbot guide, this guide
+takes precedence. Some guidelines may be repeated verbatim to stress their
+importance.
+
+## Overview
+
+GitLab is built on top of [Ruby on Rails][rails], and we're using [RSpec] for all
+the backend tests, with [Capybara] for end-to-end integration testing.
+On the frontend side, we're using [Karma] and [Jasmine] for JavaScript unit and
+integration testing.
+
+Following are two great articles that everyone should read to understand what
+automated testing means, and what are its principles:
+
+- [Five Factor Testing](https://www.devmynd.com/blog/five-factor-testing): Why do we need tests?
+- [Principles of Automated Testing](http://www.lihaoyi.com/post/PrinciplesofAutomatedTesting.html): Levels of testing. Prioritize tests. Cost of tests.
+
+---
+
+## [Testing levels](testing_levels.md)
+
+Learn about the different testing levels, and how to decide at what level your
+changes should be tested.
+
+---
+
+## [Testing best practices](best_practices.md)
+
+Everything you should know about how to write good tests: RSpec, FactoryGirl,
+system tests, parameterized tests etc.
+
+---
+
+## [Frontend testing standards and style guidelines](frontend_testing.md)
+
+Everything you should know about how to write good Frontend tests: Karma,
+testing promises, stubbing etc.
+
+---
+
+## [Flaky tests](flaky_tests.md)
+
+What are flaky tests, the different kind of flaky tests we encountered, and what
+we do about them.
+
+---
+
+## [GitLab tests in the Continuous Integration (CI) context](ci.md)
+
+How GitLab test suite is run in the CI context: setup, caches, artifacts,
+parallelization, monitoring.
+
+---
+
+## [Testing Rake tasks](testing_rake_tasks.md)
+
+Everything you should know about how to test Rake tasks.
+
+---
+
+## Spinach (feature) tests
+
+GitLab [moved from Cucumber to Spinach](https://github.com/gitlabhq/gitlabhq/pull/1426)
+for its feature/integration tests in September 2012.
+
+As of March 2016, we are [trying to avoid adding new Spinach
+tests](https://gitlab.com/gitlab-org/gitlab-ce/issues/14121) going forward,
+opting for [RSpec feature](#features-integration) specs.
+
+Adding new Spinach scenarios is acceptable _only if_ the new scenario requires
+no more than one new `step` definition. If more than that is required, the
+test should be re-implemented using RSpec instead.
+
+---
+
+[Return to Development documentation](../README.md)
+
+[^1]: /ci/yaml/README.html#dependencies
+
+[RSpec]: https://github.com/rspec/rspec-rails#feature-specs
+[Capybara]: https://github.com/teamcapybara/capybara
+[Karma]: http://karma-runner.github.io/
+[Jasmine]: https://jasmine.github.io/

doc/development/testing_guide/testing_levels.md

+# Testing levels
+
+![Testing priority triangle](img/testing_triangle.png)
+
+_This diagram demonstrates the relative priority of each test type we use. `e2e` stands for end-to-end._
+
+## Unit tests
+
+Formal definition: https://en.wikipedia.org/wiki/Unit_testing
+
+These kind of tests ensure that a single unit of code (a method) works as
+expected (given an input, it has a predictable output). These tests should be
+isolated as much as possible. For example, model methods that don't do anything
+with the database shouldn't need a DB record. Classes that don't need database
+records should use stubs/doubles as much as possible.
+
+| Code path | Tests path | Testing engine | Notes |
+| --------- | ---------- | -------------- | ----- |
+| `app/finders/` | `spec/finders/` | RSpec | |
+| `app/helpers/` | `spec/helpers/` | RSpec | |
+| `app/db/{post_,}migrate/` | `spec/migrations/` | RSpec | More details at [`spec/migrations/README.md`](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/spec/migrations/README.md). |
+| `app/policies/` | `spec/policies/` | RSpec | |
+| `app/presenters/` | `spec/presenters/` | RSpec | |
+| `app/routing/` | `spec/routing/` | RSpec | |
+| `app/serializers/` | `spec/serializers/` | RSpec | |
+| `app/services/` | `spec/services/` | RSpec | |
+| `app/tasks/` | `spec/tasks/` | RSpec | |
+| `app/uploaders/` | `spec/uploaders/` | RSpec | |
+| `app/views/` | `spec/views/` | RSpec | |
+| `app/workers/` | `spec/workers/` | RSpec | |
+| `app/assets/javascripts/` | `spec/javascripts/` | Karma | More details in the [Frontent Testing guide](frontend_testing.md) section. |
+
+## Integration tests
+
+Formal definition: https://en.wikipedia.org/wiki/Integration_testing
+
+These kind of tests ensure that individual parts of the application work well together, without the overhead of the actual app environment (i.e. the browser). These tests should assert at the request/response level: status code, headers, body. They're useful to test permissions, redirections, what view is rendered etc.
+
+| Code path | Tests path | Testing engine | Notes |
+| --------- | ---------- | -------------- | ----- |
+| `app/controllers/` | `spec/controllers/` | RSpec | |
+| `app/mailers/` | `spec/mailers/` | RSpec | |
+| `lib/api/` | `spec/requests/api/` | RSpec | |
+| `lib/ci/api/` | `spec/requests/ci/api/` | RSpec | |
+| `app/assets/javascripts/` | `spec/javascripts/` | Karma | More details in the [JavaScript](#javascript) section. |
+
+### About controller tests
+
+In an ideal world, controllers should be thin. However, when this is not the
+case, it's acceptable to write a system/feature test without JavaScript instead
+of a controller test. The reason is that testing a fat controller usually
+involves a lot of stubbing, things like:
+
+```ruby
+controller.instance_variable_set(:@user, user)
+```
+
+and use methods which are deprecated in Rails 5 ([#23768]).
+
+[#23768]: https://gitlab.com/gitlab-org/gitlab-ce/issues/23768
+
+### About Karma
+
+As you may have noticed, Karma is both in the Unit tests and the Integration
+tests category. That's because Karma is a tool that provides an environment to
+run JavaScript tests, so you can either run unit tests (e.g. test a single
+JavaScript method), or integration tests (e.g. test a component that is composed
+of multiple components).
+
+## System tests or Feature tests
+
+Formal definition: https://en.wikipedia.org/wiki/System_testing.
+
+These kind of tests ensure the application works as expected from a user point
+of view (aka black-box testing). These tests should test a happy path for a
+given page or set of pages, and a test case should be added for any regression
+that couldn't have been caught at lower levels with better tests (i.e. if a
+regression is found, regression tests should be added at the lowest-level
+possible).
+
+| Tests path | Testing engine | Notes |
+| ---------- | -------------- | ----- |
+| `spec/features/` | [Capybara] + [RSpec] | If your spec has the `:js` metadata, the browser driver will be [Poltergeist], otherwise it's using [RackTest]. |
+| `features/` | Spinach | Spinach tests are deprecated, [you shouldn't add new Spinach tests](#spinach-feature-tests). |
+
+### Consider **not** writing a system test!
+
+If we're confident that the low-level components work well (and we should be if
+we have enough Unit & Integration tests), we shouldn't need to duplicate their
+thorough testing at the System test level.
+
+It's very easy to add tests, but a lot harder to remove or improve tests, so one
+should take care of not introducing too many (slow and duplicated) specs.
+
+The reasons why we should follow these best practices are as follows:
+
+- System tests are slow to run since they spin up the entire application stack
+  in a headless browser, and even slower when they integrate a JS driver
+- When system tests run with a JavaScript driver, the tests are run in a
+  different thread than the application. This means it does not share a
+  database connection and your test will have to commit the transactions in
+  order for the running application to see the data (and vice-versa). In that
+  case we need to truncate the database after each spec instead of simply
+  rolling back a transaction (the faster strategy that's in use for other kind
+  of tests). This is slower than transactions, however, so we want to use
+  truncation only when necessary.
+
+[Poltergeist]: https://github.com/teamcapybara/capybara#poltergeist
+[RackTest]: https://github.com/teamcapybara/capybara#racktest
+
+## Black-box tests or End-to-end tests
+
+GitLab consists of [multiple pieces] such as [GitLab Shell], [GitLab Workhorse],
+[Gitaly], [GitLab Pages], [GitLab Runner], and GitLab Rails. All theses pieces
+are configured and packaged by [GitLab Omnibus].
+
+[GitLab QA] is a tool that allows to test that all these pieces integrate well
+together by building a Docker image for a given version of GitLab Rails and
+running feature tests (i.e. using Capybara) against it.
+
+The actual test scenarios and steps are [part of GitLab Rails] so that they're
+always in-sync with the codebase.
+
+[multiple pieces]: ../architecture.md#components
+[GitLab Shell]: https://gitlab.com/gitlab-org/gitlab-shell
+[GitLab Workhorse]: https://gitlab.com/gitlab-org/gitlab-workhorse
+[Gitaly]: https://gitlab.com/gitlab-org/gitaly
+[GitLab Pages]: https://gitlab.com/gitlab-org/gitlab-pages
+[GitLab Runner]: https://gitlab.com/gitlab-org/gitlab-ci-multi-runner
+[GitLab Omnibus]: https://gitlab.com/gitlab-org/omnibus-gitlab
+[GitLab QA]: https://gitlab.com/gitlab-org/gitlab-qa
+[part of GitLab Rails]: https://gitlab.com/gitlab-org/gitlab-ce/tree/master/qa
+
+## EE-specific tests
+
+EE-specific tests follows the same organization, but under the `spec/ee` folder.
+
+## How to test at the correct level?
+
+As many things in life, deciding what to test at each level of testing is a
+trade-off:
+
+- Unit tests are usually cheap, and you should consider them like the basement
+  of your house: you need them to be confident that your code is behaving
+  correctly. However if you run only unit tests without integration / system
+  tests, you might [miss] the [big] [picture]!
+- Integration tests are a bit more expensive, but don't abuse them. A system test
+  is often better than an integration test that is stubbing a lot of internals.
+- System tests are expensive (compared to unit tests), even more if they require
+  a JavaScript driver. Make sure to follow the guidelines in the [Speed](#test-speed)
+  section.
+
+Another way to see it is to think about the "cost of tests", this is well
+explained [in this article][tests-cost] and the basic idea is that the cost of a
+test includes:
+
+- The time it takes to write the test
+- The time it takes to run the test every time the suite runs
+- The time it takes to understand the test
+- The time it takes to fix the test if it breaks and the underlying code is OK
+- Maybe, the time it takes to change the code to make the code testable.
+
+### Frontend-related tests
+
+There are cases where the behaviour you are testing is not worth the time spent
+running the full application, for example, if you are testing styling, animation,
+edge cases or small actions that don't involve the backend,
+you should write an integration test using Jasmine.
+
+[miss]: https://twitter.com/ThePracticalDev/status/850748070698651649
+[big]: https://twitter.com/timbray/status/822470746773409794
+[picture]: https://twitter.com/withzombies/status/829716565834752000
+[tests-cost]: https://medium.com/table-xi/high-cost-tests-and-high-value-tests-a86e27a54df#.2ulyh3a4e
+
+---
+
+[Return to Testing documentation](index.md)

doc/development/testing_guide/testing_rake_tasks.md

+## Testing Rake tasks
+
+To make testing Rake tasks a little easier, there is a helper that can be included
+in lieu of the standard Spec helper. Instead of `require 'spec_helper'`, use
+`require 'rake_helper'`. The helper includes `spec_helper` for you, and configures
+a few other things to make testing Rake tasks easier.
+
+At a minimum, requiring the Rake helper will redirect `stdout`, include the
+runtime task helpers, and include the `RakeHelpers` Spec support module.
+
+The `RakeHelpers` module exposes a `run_rake_task(<task>)` method to make
+executing tasks simple. See `spec/support/rake_helpers.rb` for all available
+methods.
+
+Example:
+
+```ruby
+require 'rake_helper'
+
+describe 'gitlab:shell rake tasks' do
+  before do
+    Rake.application.rake_require 'tasks/gitlab/shell'
+
+    stub_warn_user_is_not_gitlab
+  end
+
+ describe 'install task' do
+    it 'invokes create_hooks task' do
+      expect(Rake::Task['gitlab:shell:create_hooks']).to receive(:invoke)
+
+      run_rake_task('gitlab:shell:install')
+    end
+  end
+end
+```
+
+---
+
+[Return to Testing documentation](index.md)