JSVerify

Looks interesting. It's  a "property-based teting library".

http://jsverify.github.io/

It comes from Haskell's quickcheck. Given a specification for a function then it checks that the function meets the spec for a number of randoom inputs and outputs .

At first glance, I haven't worked out how you define the spec without writing the actual function, but when I have time, look at it.
