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Comment by necovek

16 hours ago

A test suite never proves anything except that the code works for the test cases in it.

But yes, it would be equivalent to stating "No tests failed but I found a bug" and one would correctly deduce that test coverage is insufficient.

4 comments

necovek

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eithed  8 hours ago

These were my thoughts as well and it's nothing new, I think, regarding testing altogether:

- testing libraries (and in this case - language itself) can have bugs

- what is not covered by tests can have bugs

Additionally would add that tests verify the assumptions of coder, not expectations of the business.

To give benefit to the author - I'd read the article as: having tests for given thing ensures that it does the thing that you built the tests for. This doesn't mean that your application is free of bugs (unless you have 100% coverage, can control entire state of the system, etc) nor that it does the right thing (or that it does the thing the right way)

  • necovek  4 hours ago

    I like to differentiate between coverage by lines and semantic coverage: sometimes you need to exercise a single line multiple times to get full semantic coverage, and better semantic coverage usually beats larger line coverage for detecting problems and preventing regressions.