<!--IssueSummary start--> <details> <summary> Everyone can contribute. [Help move this issue forward](https://handbook.gitlab.com/handbook/marketing/developer-relations/contributor-success/community-contributors-workflows/#contributor-links) while earning points, leveling up and collecting rewards. </summary> - [Close this issue](https://contributors.gitlab.com/manage-issue?action=close&projectId=278964&issueIid=209794) </details> <!--IssueSummary end--> `spec/frontend/diffs/components/tree_list_spec.js` was migrated from karma to jest, during the migration we agreed that it is doing too much to be a unit test. This test should be refactored to use `shallowMount` instead of `mount`