alt Hacker NewsI realize that the example is contrived, but what is the point of writing a test of a fibonacci function if your test harness is designed to just take whatever it tells you and updates the assert to verify that what it told you is indeed what it just told you.
This assumes the code you wrote is already correct and giving the correct answer, so why bother writing tests? If, however you accept that you may have got it wrong, figure out the expected outcome through some reliable means (in this case, dig out your old TI-89), get the result and write your test to assert against a known correct value.
I wouldn't trust any tests that are written this way.
Oftentimes, the main purpose of writing the tests is to prevent future regressions. This is pretty common for instance in ML (pytorch) code. You put in some tests with various random inputs and assert it against whatever your network says the output is. That way you don't accidentally change how the network works in future refactors.