850df106

By: Tom Sydney Kerckhove <syd@cs-syd.eu>

Mutation: seed the global RNG in the spec-forest runners

The global System.Random generator was only seeded by the top-level sydTest
runner. The mutation and coverage children run a forest directly via
runSpecForestSynchronously, bypassing that seeding, so tests drawing from the
global generator (randomIO, newStdGen, ...) rather than QuickCheck's replay
seed were non-reproducible under those children — a source of spurious
mutation kills or survivors.

Move setPseudorandomness down into Test.Syd.Run and call it from all four
forest runners, so every entry point that runs a forest seeds the global
generator and no future entry point can bypass it.

Add a regression test, bump sydtest to 0.27.1.0, and add a changelog entry.

Timeline