The contribution docs say, new software features or changes must be unit tested, but the current test suite is a mix of unit-, integration-, system-, regression-, etc. tests.
It would be helpful to better structure different types of tests in the test suite, and to add some guidelines for testing.

Personally, I have chosen a pragmatic non-SWE approach, a la
"Tailor your tests towards checking the desired functionality of your code and not the coverage report!