Comment by eru
20 hours ago
And Hypothesis is miles ahead of QuickCheck in how it handles shrinking! Not only does it shrink automatically, it has no problem preserving invariants from generation in your shrinking; like only prime numbers or only strings that begin with a vowel etc.
QuickCheck also shrinks automatically and preserves invariants though?
Others have pointed out that QuickCheck doesn't shrink automatically. But in addition: QuickCheck's shrinking also doesn't preserve invariants (in general).
QuickCheck's shrinking is type based. There's lots of different ways to generate eg integers. Perhaps you want them in a specific range, or only prime numbers or only even numbers etc. To make QuickCheck's shrinker preserve these invariants, you'd have make a typed wrapper for each of them, and explicitly write a new shrinking strategy. It's annoying and complicated.
Hypothesis does this automatically.
No, QuickCheck very importantly does not shrink automatically. You have to write the shrinker yourself. Hypothesis, Hedgehog, proptest and a few others shrink automatically.
Yes, but instances require the user to provide shrinking while Hypothesis does not: shrinking is derived automatically.