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Unit tests as documentation

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94 points thunderbong | 1 comments | 17 Oct 24 17:22 UTC | HN request time: 0.001s | source
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lucianbr ◴[17 Oct 24 18:16 UTC] No.41872163[source]▶
One - unit tests explain nothing. They show what the output should be for a given input, but not why, or how you get there. I'm surprised by the nonchalant claim that "unit tests explain code". Am I missing something about the meaning of the english word "explain"?

Two - so any input value outside of those in unit tests is undocumented / unspecified behavior? A documentation can contain an explanation in words, like what relation should hold between the inputs and outputs in all cases. Unit tests by their nature can only enumerate a finite number of cases.

This seems like such an obviously not great idea...

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monocasa ◴[17 Oct 24 18:34 UTC] No.41872378[source]▶
Unit tests can explain nothing. But so can paragraphs of prose.

The benefit of explanations in tests is that running them gets you closer to knowing if any of the explanations have bit rotted.

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1. mannykannot ◴[17 Oct 24 19:26 UTC] No.41872921[source]▶
> The benefit of explanations in tests is...

What you appear to have in mind here is the documentation of a test. Any documentation that correctly explains why it matters that the test should pass will likely tell you something about what the purpose of the unit is, how it is supposed to work, or what preconditions must be satisfied in order for it to work correctly, but the first bullet point in the article seems to be making a much stronger claim than that.

The observation that both tests and documentation may fail to explain their subject sheds no light on the question of whether (or to what extent) tests in themselves can explain the things they test.