T010

A new or changed test passes on the code before the change (fail-before), so it does not test the change.

Fix: Assert what the change makes different; a test for existing behavior goes in its own change with no source edits.

Status in kerf@0.1.0: reported by kerf test --gate on a diff.

A test that needs it on purpose keeps it with a reason: // kerf-allow T010: <why> in the file header (whole file) or on the line above.