An AI-written suite with 100% line coverage and 96% branch coverage still let 8 of 43 seeded bugs pass, a mutation score of 81.4%.
Every survivor sat on a boundary or a guard clause, such as a shipping threshold of exactly $75 or a coupon larger than the order.
Feeding the survivors back to the model added five tests and lifted the mutation score to 93%, so run mutation testing before you buy an AI testing platform.