How to tell if your test coverage is solid?

Petr Zaparka improving his test coverage.

That’s easy. Let’s use something like rcov. That will tell me the percentage of test coverage. And if my percentage is above 95%, I’m golden.

Well, not quite. Most of these test coverage tools cover only unit tests. 

I know that if my test coverage is solid, I can rely on tests to break when I change something. 

We recently delivered new functionality to our system, introducing a new user journey flow. The tricky thing is that the old user journey must still work for certain cases. 

We have a solid test coverage for the old flow. And ok coverage for the new flow. 

I’m about to refactor some of the old and new functionality to remove duplications, and the first thing I’m thinking is that I don’t trust the new test coverage. 

So what am I going to do today? I will improve the test coverage until I can rely on it. 

What are your plans for today?

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