Setup

The Kotest test framework is supported on all targets, including 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.

Migrating to Kotest 6

The Kotlin multiplatform setup in Kotest 6.0 has changed from previous versions. The Kotest Gradle plugin has been renamed to io.kotest. Also, the compiler plugin has been replaced with a more robust method using KSP. 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.

Install the IntelliJ Plugin

Kotest provides an IntelliJ plugin for enhanced UX, including the ability to run individual tests, tool windows to show test layouts, and jump to source.

JVM

Example Project

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

Kotest on the JVM builds atop of the JUnit Platform project which is widely supported in the JVM ecosystem.

To use the JUnit Platform support, first configure Gradle to use JUnit platform support:

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

Andd then 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.

Enhanced IDE support

For enhanced support for jump-to-source and re-running failed tests from the test results tree, in addition to installing the Kotest Intellij Plugin into your IDE, add the Kotest Gradle plugin to your build.

For example:

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

Then you can jump-to-source for tests at any level:

As well as re-run all failed tests:

Or re-run a single test from the results tree:

Kotlin/JS

Example Project

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. Note, place the KSP plugin before the Kotest plugin in the plugins block. This restriction will be fixed in a future release.

For example:

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

Example Project

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("<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

Example Project

A working native project with Linux, Windows and MacOS targets 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("<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 }
}

Alternatively, if you have the Kotest Gradle Plugin installed, you can ask Kotest to do this for you:

kotest {
   alwaysRerunTests = true
}

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

./gradlew test --rerun