testing-strategy

Testing Strategy Skill

Test Types

Type	Purpose	Speed	Coverage Target
Unit	Single function/class	Fast	80%+ business logic
Integration	Module interactions	Medium	Critical paths
E2E	Full user flows	Slow	Happy paths

Test Structure (AAA Pattern)

describe('UserService', () => {
  describe('createUser', () => {
    it('should create user with valid data', async () => {
      // Arrange
      const userData = { name: 'John', email: '[email protected]' };
      const mockRepo = createMockRepository();
      const service = new UserService(mockRepo);

      // Act
      const result = await service.createUser(userData);

      // Assert
      expect(result.id).toBeDefined();
      expect(mockRepo.save).toHaveBeenCalledWith(expect.objectContaining(userData));
    });
  });
});

Naming Convention

Pattern: should_expectedBehavior_when_condition

it('should return null when user not found', () => {});
it('should throw ValidationError when email invalid', () => {});

Test Data Factories

import { faker } from '@faker-js/faker';

export function createUser(overrides = {}) {
  return {
    id: faker.string.uuid(),
    name: faker.person.fullName(),
    email: faker.internet.email(),
    ...overrides,
  };
}

Mocking Guidelines

Mock these:

• Database repositories
• HTTP clients
• External services
• Time/Date

Don't mock:

• The class under test
• Simple value objects
• Pure functions

const mockRepo = {
  findById: jest.fn(),
  save: jest.fn(),
};
mockRepo.findById.mockResolvedValue(createUser());

Integration Test Setup

beforeAll(async () => {
  await database.migrate();
});

afterAll(async () => {
  await database.close();
});

beforeEach(async () => {
  await database.truncateAll();
});

Checklist

• Tests follow AAA pattern
• Test names describe behavior
• External dependencies mocked
• Test data uses factories
• No test interdependencies
• Coverage meets targets