The front-matter check that stops a post shipping without tags had tests for its rules but none for its exit code, so a mutant that returned 2 or always returned 1 passed. The venture-defaults module had no test that a load-time kit leaves an already-filled field alone.
Mutation catch rate: 0.60 before, 1.00 after (one mutant, bad += 2, is equivalent because the counter is only tested for truthiness). No real defects turned up in either file. The new tests cover the exit code on clean and dirty trees, the exact 160-character description boundary, and kit precedence.