Programming language: Kotlin
Tags: Tests    
Latest version: v3.4.2

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KotlinTest is a flexible and comprehensive testing tool for Kotlin.
[Full documentation](doc/reference.md)

For latest updates see [Changelog](CHANGELOG.md)


Test with Style

Write simple and beautiful tests with the StringSpec style:

class MyTests : StringSpec({
  "length should return size of string" {
    "hello".length shouldBe 5
  "startsWith should test for a prefix" {
    "world" should startWith("wor")

KotlinTest comes with several [testing styles](doc/reference.md#testing-styles) so you can choose one that fits your needs.

Multitude of Matchers

Use over 120 provided matchers to test assertions on many different types:





The withClue and asClue helpers can add extra context to assertions so failures are self explanatory:

withClue("Name should be present") { user.name shouldNotBe null }

data class HttpResponse(val status: Int, body: String)
val response = HttpResponse(200, "the content")
response.asClue {
    it.status shouldBe 200
    it.body shouldBe "the content"

Nesting is allowed in both cases and will show all available clues.

Matchers are extension methods and so your IDE will auto complete. See the [full list of matchers](doc/matchers.md) or write your own.

Let the Computer Generate Your Test Data

Use [property based testing](doc/reference.md#property-based) to test your code with automatically generated test data:

class PropertyExample: StringSpec() {
  init {
    "String size" {
      assertAll { a: String, b: String ->
        (a + b) should haveLength(a.length + b.length)

Check all the Tricky Cases With Data Driven Testing

Handle even an enormous amount of input parameter combinations easily with [data driven tests](doc/reference.md#table-driven-testing):

class StringSpecExample : StringSpec({
  "maximum of two numbers" {
        row(1, 5, 5),
        row(1, 0, 1),
        row(0, 0, 0)
    ) { a, b, max ->
      Math.max(a, b) shouldBe max

Test Exceptions

Testing for [exceptions](doc/reference.md#exceptions) is easy with KotlinTest:

val exception = shouldThrow<IllegalAccessException> {
  // code in here that you expect to throw an IllegalAccessException
exception.message should startWith("Something went wrong")

Fine Tune Test Execution

You can specify the number of invocations, parallelism, and a timeout for each test or for all tests. And you can group tests by tags or disable them conditionally. All you need is [config](doc/reference.md#config):

class MySpec : StringSpec() {

  override val defaultTestCaseConfig = TestCaseConfig(invocations = 3)

  init {
    "should use config".config(timeout = 2.seconds, invocations = 10, threads = 2, tags = setOf(Database, Linux)) {
      // ...

And More ...

This page gives you just a short overview of KotlinTest. There are many more features:

  • Test whole collections with [Inspectors](doc/reference.md#inspectors).
  • Write elegant conditions with the [matcher DSL](doc/reference.md#matchers-and-assertions): "hello".shouldHaveSubstring("ell").
  • Reuse test logic for setup or tear down, with [Listeners](doc/reference.md#listeners).
  • Test asynchronous code with [whenReady](doc/reference.md#whenReady) and non-deterministic code with [eventually](doc/nondeterministic.md) or [continually](doc/nondeterministic.md)
  • Let KotlinTest [close resources automatically](doc/reference.md#autoclose): val reader = autoClose(StringReader("xyz"))
  • Handle tricky scenarios such as System Environment with [extensions](doc/extensions.md)
  • Use the [Spring extension](doc/extensions.md#Spring) to automatically inject your spring test classes.
  • Test [Arrow](doc/extensions.md#Arrow) data types with the Arrow extension.
  • Make use of custom plugins for integrations with tools such as [Pitest](doc/plugins.md#Pitest)

See [full documentation](doc/reference.md).



To use in gradle, configure your build to use the JUnit Platform. For Gradle 4.6 and higher this is as simple as adding useJUnitPlatform() inside the tasks with type Test and then adding the KotlinTest dependency.

Groovy (build.gradle)

test {

dependencies {
  testImplementation 'io.kotlintest:kotlintest-runner-junit5:3.3.2'

Android Project (Groovy)

android.testOptions {
    unitTests.all {

dependencies {
    testImplementation 'io.kotlintest:kotlintest-runner-junit5:3.3.2'

If you are using Gradle+Kotlin, this works for both Android and non-Android projects:

Kotlin (build.gradle.kts)

tasks.withType<Test> {

dependencies {


For maven you must configure the surefire plugin for junit tests.


And then add the KotlinTest JUnit5 runner to your build.



If you want to test the latest snapshot build, setup the same way described above, change the version to the current snapshot version and add the following repository to your repositories block:

repositories {
    maven(url = "https://oss.sonatype.org/content/repositories/snapshots/")

Currently, in snapshot builds only, our artifacts and packages are using a new name: Kotest. To use them, change every instance of io.kotlintest to io.kotest, and you should be good to go.

*Note that all licence references and agreements mentioned in the kotlintest README section above are relevant to that project's source code only.