Setup

The Kotest test framework is supported on JVM, Javascript, Native and Wasm. To enable Kotest for multiple platforms, follow the steps for the platform you are targeting as detailed in the following tabs.

caution

The KMP support in Kotest 6.0 has changed from the previous versions. There is no longer a compiler plugin but a simplified setup. Please see the rest of this page for details on how to configure Kotest for KMP in Kotest 6.0 and later.

tip

When running the Gradle test task, Gradle will cache the output and report no tests executed if no source code has changed. See the section on rerunning tests for details on how to disable this behaviour.

JVM

tip

A working project with JVM support can be found here: https://github.com/kotest/kotest-examples

Kotest on the JVM has two ways for running tests. One uses the Kotest gradle plugin, which provides detailed test output in the console, and a rich experience in Intellij (in conjuction with the Intellij Kotest plugin). The other option uses the JUnit Platform gradle plugin which is ubiquitous in the JVM ecosystem but lacks some features of the Kotest gradle plugin.

To use the Kotest gradle plugin, add the following to your build.gradle.kts file:

plugins {
   id("io.kotest") version "<kotest-version>"
}

Add the following dependency to your build:

dependencies {
   testImplementation("io.kotest:kotest-framework-engine:<kotest-version>")
}

And then execute the jvmKotest task in gradle, or run tests directly from the IDE.

To use the JUnit Platform plugin, add the following to your build.gradle.kts file:

tasks.withType<Test>().configureEach {
   useJUnitPlatform()
}

Add the following dependency to your build:

dependencies {
   testImplementation("io.kotest:kotest-runner-junit5:<kotest-version>")
}

And then execute the test task in gradle, or run tests directly from the IDE.

Kotlin/JS

tip

A working JS project can be found here: https://github.com/kotest/kotest-examples

Add the Kotest gradle plugin and Google KSP plugin to to your build.

For example:

plugins {
   id("io.kotest") version "<kotest-version>"
   id("com.google.devtools.ksp") version "<kotlin-verson>-<ksp-version>"
}

Add the kotest-framework-engine dependency to your commonTest or jsTest source set:

kotlin {
   js()
   sourceSets {
      commonTest {
         dependencies {
            implementation("io.kotest:kotest-framework-engine:<kotest-version>")
         }
      }
   }
}

Tests can be placed in either commonTest or jsTest. Run your tests using the jsTest gradle task.

note

The JS test engine is feature limited when compared to the JVM test engine. The major restriction is that annotation based configuration will not work as Kotlin does not expose annotations at runtime to JS code.

Kotlin/WasmJS

tip

A working WasmJS project can be found here: https://github.com/kotest/kotest-examples

Add the Kotest gradle plugin and Google KSP plugin to to your build.

For example:

plugins {
   id("io.kotest") version "<kotest-version>"
   id("com.google.devtools.ksp") version "<kotlin-verson>-<ksp-version>"
}

Add the kotest-framework-engine dependency to your commonTest or wasmJsTest source set:

kotlin {
   wasmJs()
   sourceSets {
      commonTest {
         dependencies {
            implementation("io.kotest:kotest-framework-engine:<kotest-version>")
         }
      }
   }
}

Tests can be placed in either commonTest or wasmJsTest. Run your tests using the wasmJsTest gradle task.

note

The WasmJS test engine is feature limited when compared to the JVM test engine. The major restriction is that annotation based configuration will not work as Kotlin does not expose annotations at runtime to Wasm code.

Kotlin/Native

tip

A working native project with linux, windows and macos configured, with unit and data driven test examples, can be found here: https://github.com/kotest/kotest-examples

Add the Kotest gradle plugin and Google KSP plugin to to your build.

For example:

plugins {
   id("io.kotest") version "<kotest-version>"
   id("com.google.devtools.ksp") version "<kotlin-verson>-<ksp-version>"
}

Add the kotest-framework-engine dependency to your commonTest, nativeTest or platform specific sourceset:

kotlin {
   linuxX64() // add any supported native target
   sourceSets {
      commonTest {
         dependencies {
            implementation("io.kotest:kotest-framework-engine:<kotest-version>")
         }
      }
   }
}

Tests can be placed in either commonTest or a specific native sourceset. Run your tests using the standard test tasks, for example linuxX86Test.

note

The native test engine is feature limited when compared to the JVM test engine. The major restriction is that annotation based configuration will not work as Kotlin does not expose annotations at runtime to native code.

Android

info

Currently, only Unit tests are supported in Kotest. The following steps enable Kotest to be used for unit tests - where the Android framework is not needed or is mocked - and that usually reside in the src/test folder of your module.

Kotest on Android uses the JUnit Platform gradle plugin. This requires configuring the android test options block in your build file and then adding the Kotest junit5 runner dependency.

android.testOptions {
   unitTests.all {
      it.useJUnitPlatform()
   }
}

dependencies {
   testImplementation 'io.kotest:kotest-runner-junit5:version'
}

tip

A working Android project with unit and data driven test examples, can be found here: https://github.com/kotest/kotest-examples

Multiplatform

tip

A working multiplatform project with JVM, JS and native targets, and unit and data driven test examples, can be found here: https://github.com/kotest/kotest-examples

Add the Kotest gradle plugin and Google KSP plugin to to your build.

For example:

plugins {
   id("io.kotest") version "<kotest-version>"
   id("com.google.devtools.ksp") version "<kotlin-verson>-<ksp-version>"
}

Add the kotest-framework-engine dependency to your commonTest source set:

kotlin {
   sourceSets {
      commonTest {
         dependencies {
            implementation("io.kotest:kotest-framework-engine:<kotest-version>")
         }
      }
   }
}

Tests can be placed in either commonTest or a platform specific directory such as jsTest or macosX64Test etc. Run your tests using the gradle check task, or a platform specific test task such as macosX64Test

note

The JS, Wasm and native test engines are feature limited when compared to the JVM test engine. The major restriction is that annotation based configuration will not work as Kotlin does not expose annotations at runtime to non-JVM platforms.

Re-running tests

By default, Gradle's incremental build will skip running tests if no source code has changed, marking the task as UP-TO-DATE. This can be inconvenient during debugging.

To force your tests to run every time, you can temporarily add the following configuration to your build.gradle.kts file:

tasks.withType<Test>().configureEach {
   logger.lifecycle("UP-TO-DATE check for $name is disabled, forcing it to run.")
   outputs.upToDateWhen { false }
}

Quick Alternative: For a single re-run without modifying build files, you can use the --rerun flag from the command line:

./gradlew test --rerun