Mastering Unit and Integration Testing in KMP and CMP with Kotest

Testing is crucial in Kotlin Multiplatform (KMP) to ensure reliability across platforms. This codelab explores Kotest, a powerful testing framework for Kotlin, covering test source sets (commonTest, jvmTest, iosTest) and Kotest’s integration with JUnit (JVM) and Mocha (JS). You'll set up Kotest in a KMP and Compose Multiplatform (CMP) project, run tests across platforms, and learn different test styles (FunSpec, DescribeSpec, etc.). Through hands-on exercises, you'll write unit tests using Kotest matchers, implement lifecycle hooks, explore property-based testing, configure test parallelism and timeouts, and test coroutines and concurrency. By the end, you'll have a solid foundation in multiplatform testing with Kotest to build robust, scalable applications.

Codelab Objectives

In this codelab, you’ll explore:

  • Understand test source sets in a Kotlin Multiplatform with Compose Multiplatform project
  • Differentiate commonTest and platform-specific source sets (jvmTest, iosTest)
  • Explore how Kotest integrates with test engines like JUnit (JVM) and Mocha (JS)
  • Compare Kotest with JUnit for multiplatform test scenarios
  • Set up Kotest in a KMP project and run tests on JVM and JS targets
  • Learn different Kotest test styles (FunSpec, DescribeSpec, etc.)
  • Write unit tests for shared logic using Kotest’s test matchers (shouldBe, shouldNotBe, shouldThrow)
  • Structure test suites for layered architecture in KMP apps
  • Implement test setup and teardown routines using Kotest lifecycle hooks
  • Use beforeTest, afterTest, beforeSpec, and afterSpec for test routines
  • Explore property-based testing to verify invariants and edge cases
  • Leverage Kotest’s extensive assertion library to write clear and expressive tests
  • Configure Kotest tests with parallelism, timeouts, and invocations
  • Use non-deterministic testing functions like eventually to repeatedly check a condition until it passes
  • Test suspending functions and concurrency with Kotest coroutine support
  • Control coroutine execution using KotlinX Coroutines Test
  • Utilize TestCoroutineDispatcher to manage coroutine timing in tests

Codelab Content

Meet the instructor

Sahar Asadian

Content Author & Course Instructor

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