Optimize reviewing-changes skill (#6099)

Co-authored-by: Claude <noreply@anthropic.com>
Co-authored-by: claude[bot] <209825114+claude[bot]@users.noreply.github.com>

.claude/skills/reviewing-changes/reference/testing-patterns.md

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+# Testing Patterns Quick Reference
+
+Quick reference for Bitwarden Android testing patterns during code reviews. For comprehensive details, read `docs/ARCHITECTURE.md` and `docs/STYLE_AND_BEST_PRACTICES.md`.
+
+## ViewModel Tests
+
+**✅ GOOD - Tests behavior**:
+```kotlin
+@Test
+fun `when login succeeds then state updates to success`() = runTest {
+    // Arrange
+    val viewModel = LoginViewModel(mockRepository)
+    coEvery { mockRepository.login(any(), any()) } returns Result.success(User())
+
+    // Act
+    viewModel.onLoginClicked("user@example.com", "password")
+
+    // Assert
+    viewModel.state.test {
+        assertEquals(LoginState.Loading, awaitItem())
+        assertEquals(LoginState.Success, awaitItem())
+    }
+}
+```
+
+**❌ BAD - Tests implementation**:
+```kotlin
+@Test
+fun `repository is called with correct parameters`() {
+    // ❌ This tests implementation details, not behavior
+    viewModel.onLoginClicked("user", "pass")
+    coVerify { mockRepository.login("user", "pass") }
+}
+```
+
+**Key Rules**:
+- Test behavior, not implementation
+- Use `runTest` for coroutine tests
+- Use Turbine for Flow testing
+- Use MockK for mocking
+
+---
+
+## Repository Tests
+
+**✅ GOOD - Tests data transformations**:
+```kotlin
+@Test
+fun `fetchItems maps API response to domain model`() = runTest {
+    // Arrange
+    val apiResponse = listOf(ApiItem(id = "1", name = "Test"))
+    coEvery { apiService.getItems() } returns apiResponse
+
+    // Act
+    val result = repository.fetchItems()
+
+    // Assert
+    assertTrue(result.isSuccess)
+    assertEquals(
+        listOf(DomainItem(id = "1", name = "Test")),
+        result.getOrThrow()
+    )
+}
+```
+
+**Key Rules**:
+- Test data transformations
+- Test error handling (network failures, API errors)
+- Test caching behavior if applicable
+- Mock API services and databases
+
+Reference: Project uses JUnit 5, MockK, Turbine, kotlinx-coroutines-test
+
+---
+
+## Null Safety
+
+**✅ GOOD - Safe handling**:
+```kotlin
+// Safe call with elvis operator
+val result = apiService.getData() ?: return State.Error("No data")
+
+// Let with safe call
+intent?.getStringExtra("key")?.let { value ->
+    processValue(value)
+}
+
+// Require with message
+val data = requireNotNull(response.data) { "Response data must not be null" }
+```
+
+**❌ BAD - Unsafe assertions**:
+```kotlin
+// ❌ Unsafe - can crash
+val result = apiService.getData()!!
+
+// ❌ Platform type unchecked
+val intent: Intent = getIntent()  // Could be null from Java
+val value = intent.getStringExtra("key")  // Potential NPE
+```
+
+**Key Rules**:
+- Avoid `!!` unless safety is guaranteed (rare)
+- Handle platform types with explicit nullability
+- Use safe calls (`?.`), elvis operator (`?:`), or explicit checks
+- Use `requireNotNull` with descriptive message if crash is acceptable
+
+---
+
+## Quick Checklist
+
+### Testing
+- [ ] ViewModels have unit tests?
+- [ ] Tests verify behavior, not implementation?
+- [ ] Edge cases covered?
+- [ ] Error scenarios tested?
+
+### Code Quality
+- [ ] Null safety handled properly (no `!!` without guarantee)?
+- [ ] Public APIs have KDoc?
+- [ ] Following naming conventions?
+
+---
+
+For comprehensive details, always refer to:
+- `docs/ARCHITECTURE.md` - Full architecture patterns
+- `docs/STYLE_AND_BEST_PRACTICES.md` - Complete style guide