Hi there. Why would you expect 5000+ tests, or anything more than 100? It seems like the number of tests that is the "right" number would be very dependent on the size of the codebase, which wasn't mentioned in the article.

We write tests when new code is added, or a bug is fixed and we want to make sure it doesn't reappear. Hopefully we add new tests without prompting, because that's the right thing to do, but our coverage enforcement will goad us into writing tests if we forget. Ideally, new code should be testable by only a few tests -- if it requires more, then it's probably too complicated and should be refactored.