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