Some more thoughts specifically about writing them tests first:

- You might have written the wrong expectation because you’re post-rationalizing the implementation.

- Is coverage branch coverage or line coverage? How often is each line/branch covered?

- Do you properly mock/stub? Is your mock reimplementing the implementation? Is your stub skipping functional parts?

- Did you reimplement parts of the implementation in your tests? This sacrifices resiliency, let‘s say if the factory seed data changes, then all your tests suddenly behave unexpededly.

- Do you have too many tests? Since tests are part of your software design they may also hinder you. Especially if you‘re going up higher in the testing pyramid.