Merge branch 'link-to-rspec-features-docs' into 'master'

Add link to external documentation of rspec-rails feature specs

See merge request !8973

doc/development/testing.md

@@ -115,6 +115,10 @@ Here are some things to keep in mind regarding test performance:
 
 ### Features / Integration
 
+GitLab uses [rspec-rails feature specs] to test features in a browser
+environment. These are [capybara] specs running on the headless [poltergeist]
+driver.
+
 - 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.
@@ -122,6 +126,10 @@ Here are some things to keep in mind regarding test performance:
 - Avoid scenario titles that add no information, such as "successfully."
 - Avoid scenario titles that repeat the feature title.
 
+[rspec-rails feature specs]: https://github.com/rspec/rspec-rails#feature-specs
+[capybara]: https://github.com/teamcapybara/capybara
+[poltergeist]: https://github.com/teampoltergeist/poltergeist
+
 ## Spinach (feature) tests
 
 GitLab [moved from Cucumber to Spinach](https://github.com/gitlabhq/gitlabhq/pull/1426)