As far as I'm aware, Hypothesis is fundamentally based around the idea of "generators are parsers of randomness" discussed in this paper; i.e. a Hypothesis "str

As far as I'm aware, Hypothesis is fundamentally based around the idea of "generators are parsers of randomness" discussed in this paper; i.e. a Hypothesis "strategy" is essentially a function from bytestrings to values. To generate random values, those strategies are run on a random bytestring; to shrink a previous value, the bytestring that lead to that value is shrunk. Haskell's "falsify" package takes a similar approach, but uses a tree of random values. This has the advantage that composite generators can run each of their parts against a different sub-tree, and hence they can be shrunk independently without interfering.