kotlin-testing

Choose a Kotest spec style like FunSpec, create mocks with mockk<Repository>(), stub calls with every or coEvery for suspend functions, and assert with matchers like shouldBe. Verify interactions using verify or coVerify after invoking the code under test.

Wrap tests in runTest from kotlinx-coroutines-test, which provides a controlled virtual-time environment. Use StandardTestDispatcher with advanceTimeBy to control delays, and never use Thread.sleep in coroutine tests.

This Skill standardizes on Kotest for its expressive spec styles, rich matchers, and built-in property-based testing. The guidance explicitly recommends picking Kotest and not mixing testing frameworks within a project.

Apply the org.jetbrains.kotlinx.kover Gradle plugin, then run ./gradlew koverHtmlReport for reports and koverVerify to enforce thresholds. The Skill targets 80% minimum coverage with higher bars for critical business logic.

Data classes are simple value holders, so use real instances as test fixtures instead of mocks. Reserve MockK for services, repositories, and other dependencies with behavior that needs isolation.

Collect emissions inside runTest using toList or a launched collector, then use advanceTimeBy to move virtual time past debounce windows. Assert on the collected emissions after time advancement.