Summary: Mutation Testing For Move: Improve Your Unit Tests

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Aptos Labs has introduced the Move Mutation Tester, a tool designed to enhance the quality of unit tests for Move smart contracts.

Key Points:

  • Why is it needed?
    Traditional code coverage tests only indicate whether a line of code is executed but do not verify if the tests properly check the intended behavior.

  • What is mutation testing?
    It introduces faults (mutants) into the source code and runs existing tests against them.

    • If tests fail due to these faults (killed mutants), it shows they are effective.
    • If tests still pass (alive mutants), it indicates blind spots in the test suite.

  • How does the tool work?

    • The tool generates mutants within selected modules or functions.
    • The --coverage flag ensures only covered code is mutated.
    • Running tests on mutants helps identify weak spots in the test suite.

  • Example Usage:

    • Running move-mutation-test run --coverage generates a report showing which mutants survived.
    • If many mutants remain alive, tests need improvement.
    • By refining the test suite and rerunning the tool, the number of killed mutants increases, improving test quality.

    Mutation testing is a valuable complement to code coverage tools, helping uncover test suite weaknesses and potential bugs. However, 100% mutation testing coverage is not always necessary—its results should be used as guidance for prioritizing test improvements.

Read more: Mutation Testing For Move: Improve Your Unit Tests | by Aptos Labs | Aptos Labs | Mar, 2025 | Medium

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