Track Discarded Test Cases

[moodmosaic]

In property-based testing, tools like QuickCheck (QC) and Hedgehog (HH) discard test cases that don't meet certain preconditions, and they track these discards to provide feedback on the test generators.

Currently, rendezvous (RV) doesn't track when test cases are discarded due to unmet preconditions. This makes it hard to know if our preconditions are too restrictive or if our generators need tweaking (specially when using custom ones via #7).

Example from #37:

(define-public (test-slice-list-bool (seq (list 127 bool)) (skip int) (n int))
  (if
    ;; Early return if the input is invalid.
    (or
      (not (and (<= 0 n) (<= n 127)))
      (not (and (<= 0 skip) (<= skip 127))))
    (ok true)
    ;; Rest of the test...
  ))

In this test, we return early if the inputs don't meet the preconditions, effectively discarding the test case. But we have no way of knowing how often this happens.

It would be helpful if RV could track and report discarded test cases, similar to how guard works in Hedgehog (example 1, example 2, example 3).

[moodmosaic]

Resolved by #40.