write-unit-tests

Testing & Quality

Use when writing or modifying unit tests in the Alkaa project — triggers on tasks like "add a test", "write tests for X", "test this ViewModel", "cover this use case with tests", or "add unit test coverage".

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Write Unit Tests

Overview

Unit tests in Alkaa are multiplatform-first, fake-based, and structured around a single scenario per test. Tests live in commonTest and run fastest via ./gradlew desktopTest.

Structure

Given / When / Then — Use comments to separate the three blocks in every test → see references/TEST_EXAMPLES.md
Backtick names — Start with test if or check if, describe the specific condition and expected outcome
One scenario per test — Split side effects, error paths, and edge cases into separate tests
Fakes only — Never mocks for domain interfaces → see references/FAKE_PATTERNS.md for all three fake patterns
CoroutinesTestDispatcher — Delegate by CoroutinesTestDispatcherImpl() for any coroutine-using test class → see references/TEST_EXAMPLES.md
ViewModel test setup → see references/TEST_EXAMPLES.md
Use case / repository test setup → see references/TEST_EXAMPLES.md

Naming

✅ `test if when load tasks fails the error state is returned`
✅ `test if task is updated as completed`
✅ `test if category without name is not added`
❌ testUpdateTask()
❌ test1()

Rules

Rule	Details
Fakes over mocks	Only use mocks for Android/Framework types you cannot interface (e.g., `Context`)
CoroutinesTestDispatcher	Delegate `by CoroutinesTestDispatcherImpl()` for any coroutine-using test class
ViewModel at field level	Construct ViewModel at field level, not inside `@BeforeTest`
`runTest` for suspend	Use `= runTest { }` for all suspend test bodies
`flow.first()`	Collect current state with `flow.first()`
`require()` for narrowing	Use `require(state is X)` before accessing state-specific properties
`@BeforeTest` cleanup	Call `clean()` on every fake to reset state between tests

Common Mistakes

Mistake	Fix
Using mocks for domain interfaces	Create a fake implementing the interface
Forgetting `CoroutinesTestDispatcher` delegation	Add `by CoroutinesTestDispatcherImpl()`
Testing multiple scenarios in one test	Split into separate `@Test` functions
Skipping `@BeforeTest` cleanup	Add `setup()` calling `clean()` on every fake
Constructing ViewModel in `@BeforeTest`	Construct at field level so it shares dispatcher context
Omitting Given/When/Then comments	Always add the three comment blocks
Vague test names like `testUpdate()`	Rename to describe the scenario and expected outcome

Related Skills

ViewModel tests → use write-viewmodel skill for ViewModel construction patterns
UI behavior tests → use write-ui-tests skill
Full user flow tests → use write-e2e-tests skill