name: Mutation testing

# Weekly, not per-push: this deliberately breaks the library seven times and
# runs a slice of the suite against each. DEBUG.md §B ranks it the
# highest-yield technique in the project, and it had been a manual discipline —
# which means it ran when somebody remembered.
#
# A failure here is a hole in the *tests*, not a bug in the code: it means the
# library can be wrong in a specific, previously-seen way and nothing says so.

on:
  schedule:
    - cron: "0 6 * * 1"  # Mondays, 06:00 UTC
  workflow_dispatch:

jobs:
  mutate:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: actions/setup-python@v5
        with:
          python-version: "3.12"
      - name: Install
        run: |
          pip install torch --index-url https://download.pytorch.org/whl/cpu
          pip install -e ".[dev]"
      - name: Break it on purpose
        run: python scripts/mutate.py