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What is mutation testing?

Mutation testing is a way to test your automated tests. Imagine you have a unit-test or integration-test that 100% covers your code. Can you be sure your test actually would catch errors in your code? Mutation testing goes through your code and changes it slightly, like changing an operator (== into = for example), or a number (5 into a 0 for example). It then builds your code and tests it, hoping that your tests will fail (mutation killed). If the test passes the mutation is said to have survived, and the line is marked. For more explanation see Wikipedia: https://en.wikipedia.org/wiki/Mutation_testing

About dumbmutate

This is an as simple as possible implementation of this technique. There is no setup and no dependencies. Just download the binary and run it from the command-line. Works with any unit-testing framework (GoogleTest, Catch2, boosttest etc), or even without a complete framework as long as your code return a non-zero value when it fails. It is geared towards C-style languages but might work with other ones too.

Features:

  • Only command-line options needed, so could be part of a buildsystem for example. Has a threshold option to return error-code when mutations killed falls below a specified percentage.
  • Exports HTML line-by-line report and also surviving mutations to terminal, so you can go-to-code directly in your IDE.
  • Gives progress updates while running, so you can tell how long left to finish the file (in minutes).
  • Ability to mutate only part of file, i e from line 10 to line 20.
  • Only dependencies for building is CMake and a C++11 compatible compiler. No dependencies for the actual tool.

Simple example:

dumbmutate --mutate=FileToMutate.cpp --build=make --test=./test

Results will be shown both in terminal and in MutationResult.html

Demo (using doctest)

How to build dumbmutate:

cmake ./
make

Mutate specific part:

Mutate specific lines of FileToTest.cpp, line 10 to 20:

dumbmutate --mutate=FileToTest.cpp --build="make" --test="./test" --start=10 --end=20

Add threshold for percentage of killed mutations

Useful for example in a CI-solution where you could make dumbmutate return an error when the ratio of killed mutations vs survived falls below a set percentage. This example sets 80% as threshold and will return 0 when mutation-killratio is above this percentage.

dumbmutate --mutate=FileToTest.cpp --build="make" --test="./test" --threshold=80