Amazing survey. Big fan of property testing. A particularly big fan of Hedgehog. I tried writing a Hedgehog-inspired library in Rust and realized how complex

Amazing survey. Big fan of property testing. A particularly big fan of Hedgehog. I tried writing a Hedgehog-inspired library in Rust and realized how complex the underlying domain is. For example, the RNG is "splittable" [1][2] which means you can take a deterministic seed and split it in two, e.g. for parallel generators to work independently but still deterministically. The effort that has gone into this feature level is a little numbing. I have an awe similar to that of the "fast inverse square root" hack when I see code like this: -- | A predefined gamma value's needed for initializing the "root" instances of -- 'Seed'. That is, instances not produced by splitting an already existing -- instance. -- -- We choose: the odd integer closest to @2^64/φ@, where @φ = (1 + √5)/2@ is -- the golden ratio. -- goldenGamma :: Word64 goldenGamma = 0x9e3779b97f4a7c15 when realizing that those numbers don't come easily. [3] [1]: https://hackage.haskell.org/package/hedgehog-1.4/docs/src/Hedgehog.Internal.Seed.html#Seed https://hackage.haskell.org/package/hedgehog-1.4/docs/src/He... [2]: https://gee.cs.oswego.edu/dl/papers/oopsla14.pdf https://gee.cs.oswego.edu/dl/papers/oopsla14.pdf [3]: https://github.com/hedgehogqa/haskell-hedgehog/issues/191 https://github.com/hedgehogqa/haskell-hedgehog/issues/191 Wonder why most property-testing libaries don't have features like this? The libraries require training to use. And they're not that easy to write. > the current state-of-the-art when it comes to property-based testing is stateful testing via a state machine model and reusing the same sequential state machine model combined with linearisability to achieve parallel testing Okay, okay. I admit I've never performed property-based stateful testing, nor in parallel. So that may be the coolest feature out there, because it addresses one of the hardest problems in testing. But I think that yet other things have happened with modern property-testing libraries (e.g. Hypothesis, PropEr, Hedgehog, Validity): Shrinking for free [4], generators for free [5], defining the probability distribution of your sub-generators in a composable way. Maybe those features are not as significant, but they're equally missing from almost all property-test libaries. [4]: Gens N’ Roses: Appetite for Reduction • Jacob Stanley • YOW! 2017 https://www.youtube.com/watch?v=LfD0DHqpeVQ https://www.youtube.com/watch?v=LfD0DHqpeVQ [5]: https://tech.fpcomplete.com/blog/quickcheck-hedgehog-validity/ https://tech.fpcomplete.com/blog/quickcheck-hedgehog-validit...