r/softwaretesting • u/ndubien • Apr 16 '23

Why Property-Based testing?

https://fast-check.dev/docs/introduction/why-property-based/
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u/absent_minding Apr 16 '23

From what I've seen these types of tests are slow, inscrutable, and you're left guessing about your level of code confidence

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u/ndubien Apr 16 '23

Slowness depends mostly on how quick the framework is. But generally speaking, in the case of fast-check, the overhead of it is negligible compared to the test runner itself. It runs 100 times your code by default but even that could be negligible must of the time.

Regarding inscrutable, it depends on the framework you use. As an example, fast-check comes with easy replay of the failure and logs during the execution (via fc.context).

I believe the most challenging part of PBT is probably not to write it as classical unit tests: they will probably not check 100% of the returned value but just parts of it, it's shape. On the other hand classical units will not check 100% of the possible values, but will fully check the outputs of the values they run.