Enhancement: fault generation for instacheck generators

[norton-at-kpmg]

First of all - thank you for the great library. It is really helpful and easy to use.

I haven't yet looked in the implementation but I would like to ask about the possibility for an enhancement. I would like to automagically generate faulty test samples that would fail if parsed by a given EBNF grammar.

I understand this could be a general feature of test.check, test.chuck, clojure.alpha.spec.gen, etc. but I'm specifically focused on instacheck at this time.

Is this something that you have considered? Would this be of interest to others?

Thank you.

p.s. This feature is supported by Erlang's eqc QuickCheck.

http://quviq.com/documentation/eqc/index.html

fault/2

fault(Fault::gen(A), G::gen(A)) -> gen(A)

Adds a fault - generation alternative to a generator. The probability of using the faulty alternative is controlled by fault_rate/3, more_faulty/2, and less_faulty/2. If no fault rate is specified, then the faulty alternative is never used. Shrinking attempts to replace a faulty value by a freshly generated non - faulty one.