feat: add Kotlin, Android, and KMP rules, agent, skills, and command

rules/kotlin/testing.md

@@ -0,0 +1,127 @@
+---
+paths:
+  - "**/*.kt"
+  - "**/*.kts"
+---
+# Kotlin Testing
+
+> This file extends [common/testing.md](../common/testing.md) with Kotlin and Android/KMP specific content.
+
+## Test Framework
+
+- **kotlin.test** for multiplatform (KMP) — `@Test`, `assertEquals`, `assertTrue`
+- **JUnit 4/5** for Android-specific tests
+- **Turbine** for testing Flows and StateFlow
+- **kotlinx-coroutines-test** for coroutine testing (`runTest`, `TestDispatcher`)
+
+## ViewModel Testing with Turbine
+
+```kotlin
+@Test
+fun `loading state emitted then data`() = runTest {
+    val repo = FakeItemRepository(items = listOf(testItem))
+    val viewModel = ItemListViewModel(GetItemsUseCase(repo))
+
+    viewModel.state.test {
+        assertEquals(ItemListState(), awaitItem())     // initial state
+        viewModel.onEvent(ItemListEvent.Load)
+        assertTrue(awaitItem().isLoading)               // loading
+        assertEquals(listOf(testItem), awaitItem().items) // loaded
+    }
+}
+```
+
+## Fakes Over Mocks
+
+Prefer hand-written fakes over mocking frameworks:
+
+```kotlin
+class FakeItemRepository : ItemRepository {
+    private val items = mutableListOf<Item>()
+    var fetchError: Throwable? = null
+
+    override suspend fun getAll(): Result<List<Item>> {
+        fetchError?.let { return Result.failure(it) }
+        return Result.success(items.toList())
+    }
+
+    override fun observeAll(): Flow<List<Item>> = flowOf(items.toList())
+
+    fun addItem(item: Item) { items.add(item) }
+}
+```
+
+## Coroutine Testing
+
+```kotlin
+@Test
+fun `parallel operations complete`() = runTest {
+    val repo = FakeRepository()
+    val result = loadDashboard(repo)
+    advanceUntilIdle()
+    assertNotNull(result.items)
+    assertNotNull(result.stats)
+}
+```
+
+Use `runTest` — it auto-advances virtual time and provides `TestScope`.
+
+## Ktor MockEngine
+
+```kotlin
+val mockEngine = MockEngine { request ->
+    when (request.url.encodedPath) {
+        "/api/items" -> respond(
+            content = Json.encodeToString(testItems),
+            headers = headersOf(HttpHeaders.ContentType, ContentType.Application.Json.toString())
+        )
+        else -> respondError(HttpStatusCode.NotFound)
+    }
+}
+
+val client = HttpClient(mockEngine) {
+    install(ContentNegotiation) { json() }
+}
+```
+
+## Room/SQLDelight Testing
+
+- Room: Use `Room.inMemoryDatabaseBuilder()` for in-memory testing
+- SQLDelight: Use `JdbcSqliteDriver(JdbcSqliteDriver.IN_MEMORY)` for JVM tests
+
+```kotlin
+@Test
+fun `insert and query items`() = runTest {
+    val driver = JdbcSqliteDriver(JdbcSqliteDriver.IN_MEMORY)
+    Database.Schema.create(driver)
+    val db = Database(driver)
+
+    db.itemQueries.insert("1", "Sample Item", "description")
+    val items = db.itemQueries.getAll().executeAsList()
+    assertEquals(1, items.size)
+}
+```
+
+## Test Naming
+
+Use backtick-quoted descriptive names:
+
+```kotlin
+@Test
+fun `search with empty query returns all items`() = runTest { }
+
+@Test
+fun `delete item emits updated list without deleted item`() = runTest { }
+```
+
+## Test Organization
+
+```
+src/
+├── commonTest/kotlin/     # Shared tests (ViewModel, UseCase, Repository)
+├── androidTest/kotlin/    # Android unit tests (JUnit)
+├── androidInstrumentedTest/kotlin/  # Instrumented tests (Room, UI)
+└── iosTest/kotlin/        # iOS-specific tests
+```
+
+Minimum test coverage: ViewModel + UseCase for every feature.