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
| Layer |
Purpose |
| Unit |
local algorithm and value contracts |
| Component |
real module behavior with owned dependencies |
| Integration |
external protocol, persistence, serialization, process boundaries |
| Contract |
shared behavior for every adapter/provider |
| End-to-end |
public workflow through production composition |
<project>-test |
whole-project migration parity and differential acceptance |
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.
1---2name: kotlin-testing3description: Design high-value Kotlin tests across unit, integration, coroutine, property, contract, adapter, end-to-end, load, and regression layers using JUnit, Kotest, MockK, Turbine, Testcontainers, or project-native tools. Use to create or assess Kotlin tests, fixtures, coverage, determinism, mutation sensitivity, and whole-project acceptance modules.4license: Apache-2.05---67# Kotlin Testing89Tests prove observable contracts. Coverage measures exercised structure but does not prove migration completeness or behavioral equivalence.1011## Test design1213- Name the contract, source test, defect, risk, or incident each test protects.14- Assert values, typed failures, ordering, state transitions, side effects, call counts, serialization bytes, cleanup, or externally observable timing boundaries.15- Prefer real values and fakes at owned boundaries. Mock only costly or nondeterministic collaborators.16- Use table/property tests for input partitions; retain each source case identity during migrations.17- For coroutines, use virtual time and event-driven coordination. Never use unbounded waits or fixed sleeps as synchronization.18- Reuse adapter conformance suites so every implementation receives the same contract assertions plus adapter-native tests.19- Keep fixtures versioned and deterministic. Record seeds, locale, timezone, encoding, and platform assumptions.2021## Test layers2223| Layer | Purpose |24|---|---|25| Unit | local algorithm and value contracts |26| Component | real module behavior with owned dependencies |27| Integration | external protocol, persistence, serialization, process boundaries |28| Contract | shared behavior for every adapter/provider |29| End-to-end | public workflow through production composition |30| `<project>-test` | whole-project migration parity and differential acceptance |3132## Migration rule3334Production 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.3536## Quality gates3738```bash39./gradlew --no-daemon test40./gradlew --no-daemon check41```4243Add 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.44
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