Merge branch 'alberts-document-order-dependent-flaky-test' into 'master'

Document order-dependent flaky tests

See merge request gitlab-org/gitlab!59369

doc/development/testing_guide/flaky_tests.md

@@ -76,6 +76,33 @@ For instance `RETRIES=1 bin/rspec ...` would retry the failing examples once.
   - [Replace FFaker factory data with sequences](https://gitlab.com/gitlab-org/gitlab-foss/-/issues/29643): <https://gitlab.com/gitlab-org/gitlab-foss/-/merge_requests/10184>
   - [Transient failure in spec/finders/issues_finder_spec.rb](https://gitlab.com/gitlab-org/gitlab-foss/-/issues/30211#note_26707685): <https://gitlab.com/gitlab-org/gitlab-foss/-/merge_requests/10404>
 
+### Order-dependent flaky tests
+
+These flaky tests can fail depending on the order they run with other tests. For example:
+
+- <https://gitlab.com/gitlab-org/gitlab/-/issues/327668>
+
+To identify the tests that lead to such failure, we can use `rspec --bisect`,
+which would give us the minimal test combination to reproduce the failure:
+
+```shell
+rspec --bisect ee/spec/services/ee/merge_requests/update_service_spec.rb ee/spec/services/ee/notes/quick_actions_service_spec.rb ee/spec/services/epic_links/create_service_spec.rb  ee/spec/services/ee/issuable/bulk_update_service_spec.rb
+Bisect started using options: "ee/spec/services/ee/merge_requests/update_service_spec.rb ee/spec/services/ee/notes/quick_actions_service_spec.rb ee/spec/services/epic_links/create_service_spec.rb ee/spec/services/ee/issuable/bulk_update_service_spec.rb"
+Running suite to find failures... (2 minutes 18.4 seconds)
+Starting bisect with 3 failing examples and 144 non-failing examples.
+Checking that failure(s) are order-dependent... failure appears to be order-dependent
+
+Round 1: bisecting over non-failing examples 1-144 . ignoring examples 1-72 (1 minute 11.33 seconds)
+...
+Round 7: bisecting over non-failing examples 132-133 . ignoring example 132 (43.78 seconds)
+Bisect complete! Reduced necessary non-failing examples from 144 to 1 in 8 minutes 31 seconds.
+
+The minimal reproduction command is:
+  rspec ./ee/spec/services/ee/issuable/bulk_update_service_spec.rb[1:2:1:1:1:1,1:2:1:2:1:1,1:2:1:3:1] ./ee/spec/services/epic_links/create_service_spec.rb[1:1:2:2:6:4]
+```
+
+We can reproduce the test failure with the reproduction command above. If we change the order of the tests, the test would pass.
+
 ### Time-sensitive flaky tests
 
 - <https://gitlab.com/gitlab-org/gitlab-foss/-/merge_requests/10046>