proptest.nx

proptest.nx -- property-based testing. EFFICIENCY_ROADMAP §5.1. Runtime: sample N random inputs, run a property on each, shrink failing input to minimal example. Quickcheck / Hypothesis / proptest equivalent. Property-based tests complement unit tests: where a unit test says "f(5) = 25", a property test says "forall n, f(n) >= 0 AND n*n >= n for n>=1". Covers input space unit tests miss. Usage shape (pseudocode until parse.nx grows lambdas): let cfg: *PropConfig = prop_config_new() cfg.n_trials = 100 let rc: i64 = prop_run(cfg, "divides_correctly", gen_i64, check_divide) if rc != 0 { /* failure */ } Generators + check functions are plain `func` values today; phase B introduces closure syntax so properties are one-liners. Invariants: PT1 Every failing trial is reported + shrunk before return. PT2 RNG state is DETERMINISTIC given the same seed so reproduction is trivial. PT3 Max trials cap respected; partial success (N-1 of N) counts as success + reports the failing seed.