Pitest

The Mutation Testing tool Pitest is integrated with Kotest via an extension module.

Gradle configuration

After configuring Pitest, add the io.kotest.extensions:kotest-extensions-pitest module to your dependencies as well:

    testImplementation("io.kotest:kotest-extensions-pitest:<version>")

note

Since Kotest 6.0, all extensions are published under the io.kotest group once again, with version cadence tied to main Kotest releases.

After doing that, we need to inform Pitest that we're going to use Kotest as a testPlugin:

// Assuming that you have already configured the Gradle/Maven extension
configure<PitestPluginExtension> {
    // testPlugin.set("Kotest")    // needed only with old PIT <1.6.7, otherwise having kotest-extensions-pitest on classpath is enough
    targetClasses.set(listOf("my.company.package.*"))
}

This should set everything up, and running ./gradlew pitest will generate reports in the way you configured.

Maven configuration

First of all, you need to configure the Maven Pitest plugin:

<plugin>
    <groupId>org.pitest</groupId>
    <artifactId>pitest-maven</artifactId>
    <version>${pitest-maven.version}</version>
    <configuration>
        <targetClasses>...</targetClasses>
        <coverageThreshold>...</coverageThreshold>
        ... other configurations as needed
    </configuration>
</plugin>

Then add the dependency on Pitest Kotest extension:

<dependencies>
  ... the other Kotest dependencies like kotest-runner-junit5
  <dependency>
    <groupId>io.kotest</groupId>
    <artifactId>kotest-extensions-pitest</artifactId>
    <version>${kotest-extensions-pitest.version}</version>
    <scope>test</scope>
  </dependency>
</dependencies>

This should be enough to be able to run Pitest and get the reports as described in the Maven Pitest plugin.