Test Strategy Skill

Patterns for planning and organizing test suites.

Testing Pyramid

code

        ┌─────────┐
        │   E2E   │  Few - Slow, Expensive
        ├─────────┤
        │  Integ  │  Some - Medium
        ├─────────┤
        │  Unit   │  Many - Fast, Cheap
        └─────────┘

Recommended Ratios

•Unit Tests: 70% - Fast, isolated, cheap
•Integration Tests: 20% - API and service integration
•E2E Tests: 10% - Critical user flows only

Test Organization

By Feature

code

tests/
├── auth/
│   ├── login.test.ts
│   ├── logout.test.ts
│   ├── register.test.ts
│   └── password-reset.test.ts
├── users/
│   ├── create-user.test.ts
│   ├── update-user.test.ts
│   └── delete-user.test.ts
└── orders/
    ├── create-order.test.ts
    └── order-flow.e2e.ts

By Type

code

tests/
├── unit/
│   ├── services/
│   ├── utils/
│   └── models/
├── integration/
│   ├── api/
│   └── database/
└── e2e/
    ├── flows/
    └── pages/

What to Test

Always Test

•Public API methods
•Business logic and calculations
•Error handling and edge cases
•Security-sensitive operations
•Data validation
•State transitions

Consider Testing

•Complex private methods
•Performance-critical code
•Integration points
•Configuration loading

Avoid Testing

•Third-party library internals
•Simple getters/setters
•Framework code
•Auto-generated code

Test Prioritization

P0 - Critical Path

Tests that must never fail:

•Authentication/authorization
•Payment processing
•Core business workflows
•Data integrity operations

P1 - High Priority

Tests for important features:

•CRUD operations
•Search and filtering
•Notifications
•User preferences

P2 - Normal Priority

Tests for auxiliary features:

•UI customization
•Report generation
•Export/import

Test Naming

Pattern

typescript

// should [expected behavior] when [condition]
it('should return empty array when no users exist')
it('should throw ValidationError when email is invalid')
it('should update user when data is valid')

Grouping

typescript

describe('UserService', () => {
  describe('createUser', () => {
    describe('with valid data', () => {
      it('should create user')
      it('should send welcome email')
    })

    describe('with invalid data', () => {
      it('should throw ValidationError for missing email')
      it('should throw ValidationError for invalid email format')
    })
  })
})

Test Data Management

Fixtures

typescript

// fixtures/users.ts
export const validUser = {
  email: 'test@example.com',
  name: 'Test User',
  role: 'user'
}

export const adminUser = {
  email: 'admin@example.com',
  name: 'Admin User',
  role: 'admin'
}

export const invalidUsers = {
  missingEmail: { name: 'No Email' },
  invalidEmail: { email: 'not-an-email', name: 'Bad Email' }
}

Factories

typescript

// factories/user.factory.ts
import { faker } from '@faker-js/faker'

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

// Usage
const user = createUser({ role: 'admin' })
const users = Array.from({ length: 10 }, () => createUser())

Coverage Strategy

Minimum Thresholds

json

{
  "coverageThreshold": {
    "global": {
      "branches": 80,
      "functions": 80,
      "lines": 80,
      "statements": 80
    },
    "./src/services/": {
      "branches": 90,
      "lines": 90
    }
  }
}

Focus Areas

•Business logic: 90%+
•API handlers: 80%+
•Utilities: 80%+
•UI components: 60%+

Integration

Used by:

•unit-test-developer agent
•api-test-developer agent
•e2e-test-developer agent