Infection

Infection is a mutation testing framework for PHP. It modifies the source code and reports which changes the test suite still passes, revealing gaps that line coverage cannot show.

It works with test frameworks such as PHPUnit, Codeception and PHPSpec. Its main metric is the Mutation Score Indicator (MSI), a single number that measures the quality of the test suite and can be shown as a badge. In CI, minimum MSI thresholds can fail the build, and options such as parallel runs, reuse of existing coverage and mutation of only the lines changed in a pull request keep run times short. An online playground allows it to be tried in the browser.

Infection is free and open source under the BSD 3-Clause licence.