Merge branch 'docs_troubleshoot_specs' into 'master'

Document how to troubleshoot hanging specs

See merge request gitlab-org/gitlab!81859

doc/development/testing_guide/flaky_tests.md

@@ -117,14 +117,17 @@ reproduction.
 - [Don't wait for AJAX when no AJAX request is fired](https://gitlab.com/gitlab-org/gitlab-foss/-/issues/30461): <https://gitlab.com/gitlab-org/gitlab-foss/-/merge_requests/10454>
 - [Bis](https://gitlab.com/gitlab-org/gitlab-foss/-/issues/34647): <https://gitlab.com/gitlab-org/gitlab-foss/-/merge_requests/12626>
 
-#### PhantomJS / WebKit related issues
-
-- Memory is through the roof! (Load images but block images requests!): <https://gitlab.com/gitlab-org/gitlab-foss/-/merge_requests/12003>
-
 #### Capybara expectation times out
 
 - [Test imports a project (via Sidekiq) that is growing over time, leading to timeouts when the import takes longer than 60 seconds](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/22599)
 
+### Hanging specs
+
+If a spec hangs, it might be caused by a [bug in Rails](https://github.com/rails/rails/issues/34310):
+
+- <https://gitlab.com/gitlab-org/gitlab/-/merge_requests/81112>
+- <https://gitlab.com/gitlab-org/gitlab/-/issues/337039>
+
 ## Resources
 
 - [Flaky Tests: Are You Sure You Want to Rerun Them?](https://semaphoreci.com/blog/2017/04/20/flaky-tests.html)