Merge branch 'improve-testing-documentation' into 'master'

Improve the testing documentation

Closes #29499 and #29623

See merge request !10161

2 files changed, 375 insertions, 99 deletions

diff --git a/doc/development/fe_guide/testing.md b/doc/development/fe_guide/testing.md
index 8d3513d3566..a4631fd0073 100644
--- a/doc/development/fe_guide/testing.md
+++ b/doc/development/fe_guide/testing.md
@@ -13,10 +13,19 @@ 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 tests.  For tests that rely on DOM
+framework for our JavaScript unit tests. For tests that rely on DOM
 manipulation we use fixtures which are pre-compiled from HAML source files and
 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.
+
 ### Running frontend tests
 
 `rake karma` runs the frontend-only (JavaScript) tests.
@@ -80,24 +89,23 @@ 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: true` to the
+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: true do
-    # assertions...
+it 'presents information about abuse report', :js do
+  # assertions...
 end
 
-describe "Admin::AbuseReports", js: true do
-    it 'presents information about abuse report' do
-        # assertions...
-    end
-    it 'shows buttons for adding to abuse report' 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
 ```
 
@@ -113,13 +121,12 @@ 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"
-
+  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/
diff --git a/doc/development/testing.md b/doc/development/testing.md
index 5bc958f5a96..ad540ec13db 100644
--- a/doc/development/testing.md
+++ b/doc/development/testing.md
@@ -9,52 +9,179 @@ this guide defines a rule that contradicts the thoughtbot guide, this guide
 takes precedence. Some guidelines may be repeated verbatim to stress their
 importance.
 
-## Factories
+## Definitions
+
+### 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 | |
+| `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 [JavaScript](#javascript) 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:
 
-GitLab uses [factory_girl] as a test fixture replacement.
-
-- Factory definitions live in `spec/factories/`, named using the pluralization
-  of their corresponding model (`User` factories are defined in `users.rb`).
-- There should be only one top-level factory definition per file.
-- FactoryGirl methods are mixed in to all RSpec groups. This means you can (and
-  should) call `create(...)` instead of `FactoryGirl.create(...)`.
-- Make use of [traits] to clean up definitions and usages.
-- When defining a factory, don't define attributes that are not required for the
-  resulting record to pass validation.
-- When instantiating from a factory, don't supply attributes that aren't
-  required by the test.
-- Factories don't have to be limited to `ActiveRecord` objects.
-  [See example](https://gitlab.com/gitlab-org/gitlab-ce/commit/0b8cefd3b2385a21cfed779bd659978c0402766d).
-
-[factory_girl]: https://github.com/thoughtbot/factory_girl
-[traits]: http://www.rubydoc.info/gems/factory_girl/file/GETTING_STARTED.md#Traits
-
-## JavaScript
-
-GitLab uses [Karma] to run its [Jasmine] JavaScript specs. They can be run on
-the command line via `bundle exec karma`.
-
-- 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.
-- Haml fixtures required for JavaScript tests live in
-  `spec/javascripts/fixtures`. They should contain the bare minimum amount of
-  markup necessary for the test.
-
-    > **Warning:** Keep in mind that a Rails view may change and
-    invalidate your test, but everything will still pass because your fixture
-    doesn't reflect the latest view. Because of this we encourage you to
-    generate fixtures from actual rails views whenever possible.
-
-- 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.
-
-[Karma]: https://github.com/karma-runner/karma
-[Jasmine]: https://github.com/jasmine/jasmine
+```ruby
+controller.instance_variable_set(:@user, user)
+```
 
-For more information, see the [frontend testing guide](fe_guide/testing.md).
+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). |
+
+[Capybara]: https://github.com/teamcapybara/capybara
+[RSpec]: https://github.com/rspec/rspec-rails#feature-specs
+[Poltergeist]: https://github.com/teamcapybara/capybara#poltergeist
+[RackTest]: https://github.com/teamcapybara/capybara#racktest
+
+#### Best practices
+
+- Create only the necessary records in the database
+- Test a happy path and a less happy path but that's it
+- Every other possible path should be tested with Unit or Integration tests
+- Test what's displayed on the page, not the internals of ActiveRecord models.
+  For instance, if you want to verify that a record was created, add
+  expectations that its attributes are displayed on the page, not that
+  `Model.count` increased by one.
+- It's ok to look for DOM elements but don't abuse it since it makes the tests
+  more brittle
+
+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.
+
+### 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
+
+## 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 feature 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.
+
+[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
+
+## Frontend testing
+
+Please consult the [dedicated "Frontend testing" guide](./fe_guide/testing.md).
 
 ## RSpec
 
@@ -117,53 +244,124 @@ it 'is overdue' do
 end
 ```
 
-### Test speed
+### System / Feature tests
 
-GitLab has a massive test suite that, without parallelization, can take more
-than an hour to run. It's important that we make an effort to write tests that
-are accurate and effective _as well as_ fast.
+- Feature specs should be named `ROLE_ACTION_spec.rb`, such as
+  `user_changes_password_spec.rb`.
+- Use only one `feature` block per feature spec file.
+- Use scenario titles that describe the success and failure paths.
+- Avoid scenario titles that add no information, such as "successfully".
+- Avoid scenario titles that repeat the feature title.
 
-Here are some things to keep in mind regarding test performance:
+### Matchers
 
-- `double` and `spy` are faster than `FactoryGirl.build(...)`
-- `FactoryGirl.build(...)` and `.build_stubbed` are faster than `.create`.
-- Don't `create` an object when `build`, `build_stubbed`, `attributes_for`,
-  `spy`, or `double` will do. Database persistence is slow!
-- Use `create(:empty_project)` instead of `create(:project)` when you don't need
-  the underlying Git repository. Filesystem operations are slow!
-- Don't mark a feature as requiring JavaScript (through `@javascript` in
-  Spinach or `js: true` in RSpec) unless it's _actually_ required for the test
-  to be valid. Headless browser testing is slow!
+Custom matchers should be created to clarify the intent and/or hide the
+complexity of RSpec expectations.They should be placed under
+`spec/support/matchers/`. Matchers can be placed in subfolder if they apply to
+a certain type of specs only (e.g. features, requests etc.) but shouldn't be if
+they apply to multiple type of specs.
 
-### Features / Integration
+### Shared contexts
 
-GitLab uses [rspec-rails feature specs] to test features in a browser
-environment. These are [capybara] specs running on the headless [poltergeist]
-driver.
+All shared contexts should be be placed under `spec/support/shared_contexts/`.
+Shared contexts can be placed in subfolder if they apply to a certain type of
+specs only (e.g. features, requests etc.) but shouldn't be if they apply to
+multiple type of specs.
 
-- Feature specs live in `spec/features/` and should be named
-  `ROLE_ACTION_spec.rb`, such as `user_changes_password_spec.rb`.
-- Use only one `feature` block per feature spec file.
-- Use scenario titles that describe the success and failure paths.
-- Avoid scenario titles that add no information, such as "successfully."
-- Avoid scenario titles that repeat the feature title.
+Each file should include only one context and have a descriptive name, e.g.
+`spec/support/shared_contexts/controllers/githubish_import_controller_shared_context.rb`.
 
-[rspec-rails feature specs]: https://github.com/rspec/rspec-rails#feature-specs
-[capybara]: https://github.com/teamcapybara/capybara
-[poltergeist]: https://github.com/teampoltergeist/poltergeist
+### Shared examples
 
-## Spinach (feature) tests
+All shared examples should be be placed under `spec/support/shared_examples/`.
+Shared examples can be placed in subfolder if they apply to a certain type of
+specs only (e.g. features, requests etc.) but shouldn't be if they apply to
+multiple type of specs.
 
-GitLab [moved from Cucumber to Spinach](https://github.com/gitlabhq/gitlabhq/pull/1426)
-for its feature/integration tests in September 2012.
+Each file should include only one context and have a descriptive name, e.g.
+`spec/support/shared_examples/controllers/githubish_import_controller_shared_example.rb`.
 
-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.
+### Helpers
 
-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.
+Helpers are usually modules that provide some methods to hide the complexity of
+specific RSpec examples. You can define helpers in RSpec files if they're not
+intended to be shared with other specs. Otherwise, they should be be placed
+under `spec/support/helpers/`. Helpers can be placed in subfolder if they apply
+to a certain type of specs only (e.g. features, requests etc.) but shouldn't be
+if they apply to multiple type of specs.
+
+Helpers should follow the Rails naming / namespacing convention. For instance
+`spec/support/helpers/cycle_analytics_helpers.rb` should define:
+
+```ruby
+module Spec
+  module Support
+    module Helpers
+      module CycleAnalyticsHelpers
+        def create_commit_referencing_issue(issue, branch_name: random_git_name)
+          project.repository.add_branch(user, branch_name, 'master')
+          create_commit("Commit for ##{issue.iid}", issue.project, user, branch_name)
+        end
+      end
+    end
+  end
+end
+```
+
+Helpers should not change the RSpec config. For instance, the helpers module
+described above should not include:
+
+```ruby
+RSpec.configure do |config|
+  config.include Spec::Support::Helpers::CycleAnalyticsHelpers
+end
+```
+
+### Factories
+
+GitLab uses [factory_girl] as a test fixture replacement.
+
+- Factory definitions live in `spec/factories/`, named using the pluralization
+  of their corresponding model (`User` factories are defined in `users.rb`).
+- There should be only one top-level factory definition per file.
+- FactoryGirl methods are mixed in to all RSpec groups. This means you can (and
+  should) call `create(...)` instead of `FactoryGirl.create(...)`.
+- Make use of [traits] to clean up definitions and usages.
+- When defining a factory, don't define attributes that are not required for the
+  resulting record to pass validation.
+- When instantiating from a factory, don't supply attributes that aren't
+  required by the test.
+- Factories don't have to be limited to `ActiveRecord` objects.
+  [See example](https://gitlab.com/gitlab-org/gitlab-ce/commit/0b8cefd3b2385a21cfed779bd659978c0402766d).
+
+[factory_girl]: https://github.com/thoughtbot/factory_girl
+[traits]: http://www.rubydoc.info/gems/factory_girl/file/GETTING_STARTED.md#Traits
+
+### Fixtures
+
+All fixtures should be be placed under `spec/fixtures/`.
+
+### Config
+
+RSpec config files are files that change the RSpec config (i.e.
+`RSpec.configure do |config|` blocks). They should be placed under
+`spec/support/config/`.
+
+Each file should be related to a specific domain, e.g.
+`spec/support/config/capybara.rb`, `spec/support/config/carrierwave.rb`, etc.
+
+Helpers can be included in the `spec/support/config/rspec.rb` file. If a
+helpers module applies only to a certain kind of specs, it should add modifiers
+to the `config.include` call. For instance if
+`spec/support/helpers/cycle_analytics_helpers.rb` applies to `:lib` and
+`type: :model` specs only, you would write the following:
+
+```ruby
+RSpec.configure do |config|
+  config.include Spec::Support::Helpers::CycleAnalyticsHelpers, :lib
+  config.include Spec::Support::Helpers::CycleAnalyticsHelpers, type: :model
+end
+```
 
 ## Testing Rake Tasks
 
@@ -201,6 +399,77 @@ describe 'gitlab:shell rake tasks' do
 end
 ```
 
+## Test speed
+
+GitLab has a massive test suite that, without [parallelization], can take hours
+to run. It's important that we make an effort to write tests that are accurate
+and effective _as well as_ fast.
+
+Here are some things to keep in mind regarding test performance:
+
+- `double` and `spy` are faster than `FactoryGirl.build(...)`
+- `FactoryGirl.build(...)` and `.build_stubbed` are faster than `.create`.
+- Don't `create` an object when `build`, `build_stubbed`, `attributes_for`,
+  `spy`, or `double` will do. Database persistence is slow!
+- Use `create(:empty_project)` instead of `create(:project)` when you don't need
+  the underlying Git repository. Filesystem operations are slow!
+- Don't mark a feature as requiring JavaScript (through `@javascript` in
+  Spinach or `:js` in RSpec) unless it's _actually_ required for the test
+  to be valid. Headless browser testing is slow!
+
+[parallelization]: #test-suite-parallelization-on-the-ci
+
+### 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] and 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
+
+## 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