How to get the seed if process crashed?

[martincostello]

I'm trying to add fuzz tests to an existing code base that has a dependency on a native C DLL that I call via P/Invoke, and I'm getting an intermittent crash in that native library I'm trying to get to the bottom of.

However, because the test process crashes I'm not getting any indication of what the seed was to try and reliably reproduce the sequence of events/inputs that causes the crash because the code doesn't get as far as a failed assertion.

It doesn't seem to be quite as simple as "input A make function B crash" as from some manual logging it appears that which test/function is crashing the process varies, so I think I need to apply the seed to the whole process to get a repro I can reliably debug.

I couldn't see an obvious way to manually access the seed to log it for later re-use - is there a way to do this?

[ploeh]

I can't say how to manually access the seed, but if that's not possible, a fallback strategy might be to use Gen.sample to pre-generate test values, so that you know which values you're about to try. Perhaps you can find some inspiration in this article of mine: https://blog.ploeh.dk/2021/01/04/dynamic-test-oracles-for-rho-problems