full-stack-skills/kotlin-skills/kotlin-testing

Kotlin Testing

Tests prove observable contracts. Coverage measures exercised structure but does not prove migration completeness or behavioral equivalence.

Test design

• Name the contract, source test, defect, risk, or incident each test protects.
• Assert values, typed failures, ordering, state transitions, side effects, call counts, serialization bytes, cleanup, or externally observable timing boundaries.
• Prefer real values and fakes at owned boundaries. Mock only costly or nondeterministic collaborators.
• Use table/property tests for input partitions; retain each source case identity during migrations.
• For coroutines, use virtual time and event-driven coordination. Never use unbounded waits or fixed sleeps as synchronization.
• Reuse adapter conformance suites so every implementation receives the same contract assertions plus adapter-native tests.
• Keep fixtures versioned and deterministic. Record seeds, locale, timezone, encoding, and platform assumptions.

Test layers

Migration rule

Production modules keep local tests. A dedicated <project>-test Gradle module owns copied source fixtures, cross-module scenarios, Java/Kotlin runners, output normalization, and full differential comparison. It must not replace local tests, and local tests must not be counted as whole-project acceptance unless they actually cross the production composition boundary.

Quality gates

./gradlew --no-daemon test
./gradlew --no-daemon check

Add mutation, fuzz/property, load/soak, compatibility, or security gates according to risk. Do not weaken assertions to improve pass rate or inflate coverage with trivial tests.