What is Mutation Testing? A Practical Guide for QA Engineers
python
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Line coverage is a liar. Your tests can cover 100% of your code and still miss critical bugs. Coverage tells you which lines ran -- not which bugs your tests actually catch. Mutation testing fixes this gap. It answers a harder question: "If I introduce a bug into this code, will my tests detect it?" How Mutation Testing Works Start with correct code -- the "golden" implementation Generate mutants -- AI or tools create variants with subtle bugs (off-by-one errors, wrong operators