Mutation Testing

Mutation testing is a software testing technique that evaluates the quality of existing software tests by introducing small, intentional changes (mutations) to the source code and checking if the tests detect these changes. It helps identify weaknesses in test suites by measuring how effectively they can catch artificially introduced bugs. This method provides a quantitative measure of test effectiveness, often expressed as a mutation score.

Also known as: Mutation analysis, Mutant testing, Fault-based testing, Mutation score analysis, Mutant killing

Why learn Mutation Testing?

Developers should use mutation testing when they need to assess and improve the robustness of their unit or integration tests, particularly in safety-critical systems, financial applications, or projects with high code coverage requirements. It is valuable for identifying gaps in test suites that traditional coverage metrics might miss, ensuring tests are not just passing but actually verifying correct behavior. This technique is especially useful in test-driven development (TDD) environments or when maintaining legacy codebases to prevent regression bugs.

Learning Resources

• docs: Mutation Testing - Wikipedia
• tutorial: Introduction to Mutation Testing - Martin Fowler
• docs: Mutation Testing with PIT - Official Documentation
• video: Mutation Testing in Practice - YouTube Tutorial
• course: Practical Mutation Testing - Coursera Course