Juan-Carlos Gandhi (![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png)
juan_gandhi) wrote2020-08-23 09:18 pm
juan_gandhi) wrote2020-08-23 09:18 pm
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TWIMC: tests using random and current time
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.
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.
no subject
I am not sure I understand what one could do about it. How do you defend against this? Write a piece of code for validating the randoms provided are sufficiently random?
It makes more sense to write tests supposing the entropy is depleted. (and the rng device blocks indefinitely)
no subject
This one is basically a joke. But if people count on dispersion...
Regarding blocks indefinitely, we would be testing the RNG itself here, right?
no subject
Re: blocking indefinitely - I was thinking of /dev/random. We can deplete it, and we have seen what happens to the programs that don't think that's possible.