TWIMC: tests using random and current time

[juan_gandhi]

 So, if you think you call a function in your code, and this function returns current time, or a random number... IT'S NOT A FUNCTION. Your code is function of "random number", or "time".

So, if your code is written as something that retrieves this kind of data, to test your code, you should provide that data. Not just today, but try the time, like 10 years from now. As to "random", You provide the randomness. If your code cannot be fixed to behave as a function of those inputs, make your "random stream" or "time stream" not hard-coded, but substitutable. Mockable. And mock it in your tests. MAKE SURE that you don't provide just happy-path data. Provide anything. A sequence of 100 numbers 4 for random. Time that is 10 years from now. Or even 30 yeas from now.

Make sure that your tests don't depend on anything. Because test Must Be Reproducible.

All these things, I know, are obvious to some, and not obvious to others.

If you still have questions, ask. But don't argue. Because what I say is math. Unless you have another math (some people do), or another logic (there's plenty of them), please don't argue.

I'd be glad to see how all this changes if logic is e.g. linear. 

 

Comments

Re: Tests self-diagnostic

[sassa_nf]

It's a bug in the specification. It happens sometimes. But the tests only test the correspondence between the test and the code, not between the code and the intention.

Say:

fn is_even(x: u32) -> bool {
   is_odd(x + 1)
}

fn is_odd(x: u32) -> bool {
   x != 0 && is_even(x + 1)
}

the bug in the intention is not very easy to see. (And, by the way, is_odd(2) produces 100% code coverage, which says something about that metric).

Re: Tests self-diagnostic

[mikkim08]

It's a bug in the specification.

Разве ? По-моему, это больше похоже на "чётное количество ошибок".