Unit tests are code too and they should get some static analysis love.

Having some static analysis on the unit tests should make them more accurate especially over time (e.g. it becomes impossible to create a mock that is incoherent with the types of mocked class/interface).

The addition will be done over time. First it will be activated on a few plugins and all the identified issues will be resolved. If nothing major is identified at this point, it will enabled on all the unit tests and the baseline will be updated to include pre-existing errors.