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Came here to say I've had this exact same debate. We were writing long Python test suites to check types. I constantly (and playfully, I don't care to die on this hill) pointed out this is fully automatable with a static typing system. I remember many times being told to just read thousands of lines of uncommented tests in order to understand some thing I was trying to debug. (Don't get me started on Python stack traces!)

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I've started applying `mypy --strict` to my new python code. It caught so many issues already it's definitely worth it. Mostly in cases of uncommon error handling, some in code which was tested but under wrong assumptions and would actually fail on production. (This is a problem with "you can test types approach")

Yes, mypy is terrific, and has changed the way I write Python programs.

Taking this gradual typing tool a step further, you can run your tests with the typeguard plugin for pytest, which will dynamically check the types of most values, pointing out places where your types are a lie.

https://typeguard.readthedocs.io/en/latest/userguide.html#us...

That's amazing. Thank you for mentioning this.

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