The article uses the words "integrated" vs. "internal" shrinking.

> the raison d’être of internal shrinking: it doesn’t matter that we cannot shrink the two generators independently, because we are not shrinking generators! Instead, we just shrink the samples that feed into those generators.

Besides that it seems like falsify has many of the same features like choice of ranges and distributions.

If I understand correctly, they approximate language of inputs of a function to discover minimal (in some sense, like "shortest description length") inputs that violate relations between inputs and outputs of a function under scrutiny.

    newtype Parser a = Parser ([Word] -> (a, [Word])

Suppose I have a function which takes four string parameters, and I have a bug which means it crashes if the third is empty.

I'd rather see this in the failure report:

("ldiuhuh!skdfh", "nd#lkgjdflkgdfg", "", "dc9ofugdl ifugidlugfoidufog")

than this:

("", "", "", "")