Testing Strategy Skill

This skill provides detailed implementation guidance for testing. The core mandates (TDD, AAA, test pyramid ratios) are in the testing-strategy rule and are always active. Load this skill when you need specific patterns, tools, or language conventions.

Test Doubles Strategy

Unit Tests: Use mocks/stubs for all driven ports

• Mock repositories return pre-defined data
• Mock external APIs return successful responses
• Mock time/random for deterministic tests
• Control test environment completely

Integration Tests: Use real infrastructure

• Testcontainers spins up PostgreSQL, Redis, message queues
• Firebase emulator spins up Firebase Authentication, Cloud Firestore, Realtime Database, Cloud Storage for Firebase, Firebase Hosting, Cloud Functions, Pub/Sub, and Firebase Extensions
• Test actual database queries, connection handling, transactions
• Verify adapter implementations work with real services

Best Practice: Generate at least 2 implementations per driven port:

1. Production adapter (PostgreSQL, GCP GCS, etc.)
2. Test adapter (in-memory, fake implementation)

Test Organization

Co-located Tests (Unit & Integration)

Place tests next to the file they test. This keeps tests visible, encourages maintenance, and supports refactoring.

Naming Conventions by Language:

Language	Unit	Integration
TS/JS	framework-dependent — see note below	framework-dependent
Go	*_test.go	*_integration_test.go
Dart/Flutter	*_test.dart (in test/ mirroring lib/)	*_integration_test.dart
Python	test_*.py	test_*_integration.py
Java	*Test.java	*IT.java
Rust	#[cfg(test)] mod tests inline	tests/ at crate root

TS/JS test-naming is framework-dependent, not a single suffix. Authoritative rule: @.agents/skills/typescript-idioms/references/project-structure.md §Test Organization. Summary: Vue & Angular use *.spec.ts (CLI default); React uses *.test.tsx; generic TS, Hono, and Next.js App Router use *.test.ts (Next.js co-locates in __tests__/). Do not mix test and spec suffixes within a single package — follow that package's framework convention.

Language-Specific Overrides

Flutter: Tests live in test/ mirroring lib/ layout (Flutter's default convention, discovered by flutter test). See the flutter-idioms skill's project-structure reference.

Rust: Unit tests are inline (#[cfg(test)] mod tests at the bottom of each .rs file). This is the official Rust convention — it enables testing private functions and is how cargo test discovers unit tests. Integration tests go in tests/ at the crate root, compiled as separate crates. See the rust-idioms skill.

E2E Tests (Separate)

Place in a dedicated e2e/ folder:

• Single app: e2e/ at project root
• Monorepo: apps/e2e/ subdivided by scope: apps/e2e/api/ and apps/e2e/ui/
• Naming: {feature}-{ui/api}.e2e.test.{ext}

For interactive E2E testing, see the browser-automation skill.

Test Quality Standards

AAA Pattern Example:

// Arrange: Set up test data and mocks
const user = { id: '123', email: 'test@example.com' };
const mockRepo = createMockRepository();

// Act: Execute the code under test
const result = await userService.createUser(user);

// Assert: Verify expected outcome
expect(result.id).toBe('123');
expect(mockRepo.save).toHaveBeenCalledWith(user);

Test Naming: should [expected behavior] when [condition]

• should return 404 when user not found
• should hash password before saving to database
• should reject email with invalid format

Coverage Requirements:

• Unit tests: >85% code coverage
• Integration tests: All adapter implementations
• E2E tests: Critical user journeys

Test doubles co-location: Place mocks next to interface (e.g., storage_mock.go, taskAPI.mock.ts)