Test Analysis Extensions

Kotlin Test Frameworks Reference (JUnit 5, Kotest, MockK)

Reference data for analyzing Kotlin test code. Used by the polyglot test analysis skills.

Capability tags

Test File Identification

Assertion APIs

MockK verifications: verify(exactly = 1) { mock.method() } — counts as a state/side-effect assertion.

Sleep/Delay Patterns

Real delay inside runBlocking { } is a sleep smell; inside runTest { } it's virtual time and acceptable.

Skip/Ignore Annotations

Exception Handling — Idiomatic Alternatives

// JUnit 5:
val ex = assertThrows<InvalidOrderException> {
    service.placeOrder(emptyOrder)
}
assertEquals("at least one item", ex.message)

// Kotest:
val ex = shouldThrow<InvalidOrderException> {
    service.placeOrder(emptyOrder)
}
ex.message shouldContain "at least one item"

// AssertK:
assertFailure { service.placeOrder(emptyOrder) }
    .isInstanceOf(InvalidOrderException::class)
    .messageContains("at least one item")

Flag manual try { ... fail() } catch (e: SomeException) { ... } patterns.

Mystery Guest — Common Kotlin/Android Patterns

Integration Test Markers

• File suffix: *IT.kt, *IntegrationTest.kt, *E2ETest.kt

• Annotations: @SpringBootTest, @DataJpaTest, @Tag("integration")

• Kotest tags: tag = listOf(IntegrationTag)

• Android: androidTest/ source set is on-device/instrumented (integration); test/ is JVM (unit)

• Use of Testcontainers, embedded servers

Setup/Teardown

Tag/Trait Attributes (for test-tagging)

For JUnit 5 in Gradle, register tag filters in build.gradle.kts:

tasks.test {
    useJUnitPlatform {
        includeTags("positive")
        excludeTags("slow")
    }
}

Language-specific calibration notes

• Coroutine tests must use runTest / runBlocking at the boundary; missing wrapper makes the test silently incomplete. Flag suspend fun test bodies without a coroutine scope.

• runBlocking vs runTest: runBlocking waits in real time; runTest uses virtual time. Prefer runTest for testing time-dependent code.

• MockK verify { } without exactly = N only checks at least once. Tests asserting exact behavior should set the count.

• Kotest's forAll(...) (data-driven) is parametrized, NOT duplicate tests.

• @OptIn(ExperimentalCoroutinesApi::class) is common in coroutine tests — not a smell.

• Android @MediumTest / @LargeTest are size annotations from androidx.test.filters; treat as integration markers.

• Compose UI tests (createComposeRule) are UI integration tests.

• Bare assert(x) in tests is the Kotlin kotlin.assert — acceptable but recommend framework matchers for richer failure messages.

• shouldBe chained Kotest matchers are single conceptual assertions; do not over-count chain length.