D020 - The tooling has tests, and they run against real reports

assumed · 2026-08-19

tools/test-tools.sh pins the exit codes of verify.py and diff.py, and runs in make check.

Both tools signal through their exit code and both are consumed by CI. An exit code nobody checks is one that can silently invert - and a diff tool that stopped reporting regressions would be invisible precisely while doing the most damage, because a clean run looks like good news.

The tests degrade a real captured report rather than using a fixture: take the current output, turn one pass into a fail, assert the diff notices. A fixture drifts from the format while the tests keep passing, which is the failure mode this is guarding against in the first place.