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+# Frontend Testing
+
+There are two types of tests you'll encounter while developing frontend code
+at GitLab.  We use Karma and Jasmine for JavaScript unit testing, and RSpec
+feature tests with Capybara for integration testing.
+
+Feature tests need to be written for all new features. Regression tests ought
+to be written for all bug fixes to prevent them from recurring in the future.
+
+See [the Testing Standards and Style Guidelines](/doc/development/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 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.
+
+### 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](/doc/development/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: true` 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...
+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
+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/