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.extensions:kotest-extensions-pitest:<version>")

Note: Since pitest is an extension, we use a different maven group name (io.kotest.extensions) from the core modules.

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-jvm 
  <dependency>
    <groupId>io.kotest.extensions</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.