At the moment the PhabricatorProjectCoreTestCase does not try to call the DestructionEngine so it's not easy to propose patches in that area.

This is a note on the fridge to expand a bit the test cases:

src/applications/project/__tests__/PhabricatorProjectCoreTestCase.php

This task also aims to help reviewers on this:

D25772: Projects: improve quality of destroy workflow

So, its test plan can become just "run unit tests" and reviewers can quick approve :D lol