# Testing Strategy and Guide

Comprehensive guide to testing Changemaker Lite V2, covering unit tests, integration tests, and end-to-end testing strategies.

## Overview

**Current Status:** Phase 15 (Testing + Polish) in progress. Test infrastructure is being implemented.

This guide covers:
- Testing philosophy and strategy
- Test frameworks (Jest, Vitest, React Testing Library)
- Writing tests for API and Frontend
- Running tests and generating coverage
- Testing best practices

## Testing Philosophy

### Test Pyramid

```
       /\
      /E2E\         ← Few, high-value end-to-end tests
     /------\
    /Integration\   ← Moderate integration tests
   /------------\
  /   Unit Tests  \ ← Many, fast unit tests
 /----------------\
```

**Unit Tests (70%):**
- Test individual functions/components
- Fast execution (milliseconds)
- No external dependencies
- Easy to write and maintain

**Integration Tests (20%):**
- Test multiple units working together
- Test API routes with database
- Test user flows in frontend
- Moderate execution time

**End-to-End Tests (10%):**
- Test complete user journeys
- Test across API and frontend
- Slow execution (seconds)
- Complex setup

### Testing Principles

1. **Test Behavior, Not Implementation**
   - Test what the code does, not how it does it
   - Allows refactoring without breaking tests

2. **Arrange-Act-Assert (AAA) Pattern**
   - **Arrange:** Set up test data and mocks
   - **Act:** Execute the code under test
   - **Assert:** Verify expected behavior

3. **Independent Tests**
   - Each test runs in isolation
   - No shared state between tests
   - Tests can run in any order

4. **Fast Feedback**
   - Tests run quickly (< 1 second each)
   - Run tests in watch mode during development
   - Run full suite in CI/CD

5. **Readable Tests**
   - Clear test names describing what is tested
   - Simple setup and assertions
   - Good error messages when tests fail

## Test Frameworks

### API Testing (Jest)

**Framework:** Jest
**Location:** `api/src/**/*.test.ts`
**Config:** `api/jest.config.js`

**Installation:**
```bash
cd api
npm install --save-dev jest @types/jest ts-jest
npm install --save-dev @types/supertest supertest
```

**Configuration (jest.config.js):**
```javascript
module.exports = {
  preset: 'ts-jest',
  testEnvironment: 'node',
  roots: ['<rootDir>/src'],
  testMatch: ['**/*.test.ts'],
  collectCoverageFrom: [
    'src/**/*.{ts,tsx}',
    '!src/**/*.d.ts',
    '!src/**/*.test.ts'
  ],
  coverageThreshold: {
    global: {
      branches: 80,
      functions: 80,
      lines: 80,
      statements: 80
    }
  }
};
```

### Frontend Testing (Vitest + React Testing Library)

**Framework:** Vitest (Vite-native test runner)
**Component Testing:** React Testing Library
**Location:** `admin/src/**/*.test.tsx`, `admin/src/**/*.spec.tsx`
**Config:** `admin/vitest.config.ts`

**Installation:**
```bash
cd admin
npm install --save-dev vitest @vitest/ui
npm install --save-dev @testing-library/react @testing-library/jest-dom
npm install --save-dev @testing-library/user-event
```

**Configuration (vitest.config.ts):**
```typescript
import { defineConfig } from 'vitest/config';
import react from '@vitejs/plugin-react';

export default defineConfig({
  plugins: [react()],
  test: {
    environment: 'jsdom',
    globals: true,
    setupFiles: './src/test/setup.ts',
    coverage: {
      provider: 'v8',
      reporter: ['text', 'json', 'html'],
      exclude: [
        'node_modules/',
        'src/test/',
        '**/*.d.ts',
        '**/*.config.*',
        '**/mockData'
      ]
    }
  }
});
```

**Setup File (admin/src/test/setup.ts):**
```typescript
import '@testing-library/jest-dom';
import { expect, afterEach } from 'vitest';
import { cleanup } from '@testing-library/react';

// Cleanup after each test
afterEach(() => {
  cleanup();
});
```

## API Testing

### Unit Tests (Service Layer)

Test business logic in service files:

**Example: api/src/modules/auth/auth.service.test.ts**

```typescript
import { describe, it, expect, beforeEach, vi } from 'vitest';
import { AuthService } from './auth.service';
import { PrismaClient } from '@prisma/client';
import bcrypt from 'bcryptjs';

// Mock Prisma
vi.mock('@prisma/client');

describe('AuthService', () => {
  let authService: AuthService;
  let mockPrisma: any;

  beforeEach(() => {
    mockPrisma = {
      user: {
        findUnique: vi.fn(),
        create: vi.fn()
      }
    };
    authService = new AuthService(mockPrisma);
  });

  describe('login', () => {
    it('should return tokens for valid credentials', async () => {
      // Arrange
      const email = 'test@example.com';
      const password = 'Password123!';
      const hashedPassword = await bcrypt.hash(password, 10);

      mockPrisma.user.findUnique.mockResolvedValue({
        id: 1,
        email,
        password: hashedPassword,
        role: 'USER'
      });

      // Act
      const result = await authService.login(email, password);

      // Assert
      expect(result).toHaveProperty('accessToken');
      expect(result).toHaveProperty('refreshToken');
      expect(result.user.email).toBe(email);
    });

    it('should throw error for invalid password', async () => {
      // Arrange
      const email = 'test@example.com';
      const hashedPassword = await bcrypt.hash('correctpass', 10);

      mockPrisma.user.findUnique.mockResolvedValue({
        id: 1,
        email,
        password: hashedPassword,
        role: 'USER'
      });

      // Act & Assert
      await expect(
        authService.login(email, 'wrongpass')
      ).rejects.toThrow('Invalid credentials');
    });

    it('should throw error for non-existent user', async () => {
      // Arrange
      mockPrisma.user.findUnique.mockResolvedValue(null);

      // Act & Assert
      await expect(
        authService.login('nonexistent@example.com', 'password')
      ).rejects.toThrow('Invalid credentials');
    });
  });

  describe('register', () => {
    it('should create new user with hashed password', async () => {
      // Arrange
      const email = 'new@example.com';
      const password = 'Password123!';

      mockPrisma.user.findUnique.mockResolvedValue(null);
      mockPrisma.user.create.mockResolvedValue({
        id: 1,
        email,
        role: 'USER'
      });

      // Act
      const result = await authService.register(email, password);

      // Assert
      expect(mockPrisma.user.create).toHaveBeenCalledWith({
        data: expect.objectContaining({
          email,
          password: expect.any(String),
          role: 'USER'
        })
      });
      expect(result.user.email).toBe(email);
    });

    it('should throw error if user already exists', async () => {
      // Arrange
      mockPrisma.user.findUnique.mockResolvedValue({
        id: 1,
        email: 'existing@example.com'
      });

      // Act & Assert
      await expect(
        authService.register('existing@example.com', 'Password123!')
      ).rejects.toThrow('User already exists');
    });
  });
});
```

### Integration Tests (Routes)

Test API endpoints with database:

**Example: api/src/modules/auth/auth.routes.test.ts**

```typescript
import { describe, it, expect, beforeAll, afterAll } from 'vitest';
import request from 'supertest';
import { app } from '../../server';
import { PrismaClient } from '@prisma/client';

const prisma = new PrismaClient();

describe('Auth Routes', () => {
  beforeAll(async () => {
    // Setup test database
    await prisma.$connect();
  });

  afterAll(async () => {
    // Cleanup
    await prisma.user.deleteMany();
    await prisma.$disconnect();
  });

  describe('POST /api/auth/register', () => {
    it('should register new user', async () => {
      const response = await request(app)
        .post('/api/auth/register')
        .send({
          email: 'test@example.com',
          password: 'Password123!'
        })
        .expect(201);

      expect(response.body).toHaveProperty('accessToken');
      expect(response.body).toHaveProperty('refreshToken');
      expect(response.body.user.email).toBe('test@example.com');
    });

    it('should return 400 for invalid email', async () => {
      const response = await request(app)
        .post('/api/auth/register')
        .send({
          email: 'invalid-email',
          password: 'Password123!'
        })
        .expect(400);

      expect(response.body).toHaveProperty('error');
    });

    it('should return 409 for existing user', async () => {
      // Create user first
      await request(app)
        .post('/api/auth/register')
        .send({
          email: 'existing@example.com',
          password: 'Password123!'
        });

      // Try to create again
      const response = await request(app)
        .post('/api/auth/register')
        .send({
          email: 'existing@example.com',
          password: 'Password123!'
        })
        .expect(409);

      expect(response.body.error).toContain('already exists');
    });
  });

  describe('POST /api/auth/login', () => {
    it('should login with valid credentials', async () => {
      // Register user first
      await request(app)
        .post('/api/auth/register')
        .send({
          email: 'login@example.com',
          password: 'Password123!'
        });

      // Login
      const response = await request(app)
        .post('/api/auth/login')
        .send({
          email: 'login@example.com',
          password: 'Password123!'
        })
        .expect(200);

      expect(response.body).toHaveProperty('accessToken');
      expect(response.body).toHaveProperty('refreshToken');
    });

    it('should return 401 for invalid password', async () => {
      const response = await request(app)
        .post('/api/auth/login')
        .send({
          email: 'login@example.com',
          password: 'WrongPassword!'
        })
        .expect(401);

      expect(response.body.error).toContain('Invalid credentials');
    });
  });
});
```

### Database Testing

Use separate test database:

**Environment Variable (.env.test):**
```bash
DATABASE_URL=postgresql://changemaker_v2:password@localhost:5433/changemaker_v2_test_db
```

**Setup Script (api/src/test/setup.ts):**
```typescript
import { PrismaClient } from '@prisma/client';
import { execSync } from 'child_process';

const prisma = new PrismaClient();

export async function setupTestDatabase() {
  // Apply migrations
  execSync('npx prisma migrate deploy', {
    env: { ...process.env, DATABASE_URL: process.env.TEST_DATABASE_URL }
  });

  // Clean data
  await prisma.user.deleteMany();
  await prisma.campaign.deleteMany();
  // ... delete all tables
}

export async function teardownTestDatabase() {
  await prisma.$disconnect();
}
```

## Frontend Testing

### Component Unit Tests

Test individual React components:

**Example: admin/src/components/UserCard.test.tsx**

```typescript
import { describe, it, expect } from 'vitest';
import { render, screen } from '@testing-library/react';
import { UserCard } from './UserCard';

describe('UserCard', () => {
  it('renders user information', () => {
    const user = {
      id: 1,
      email: 'test@example.com',
      role: 'USER',
      name: 'Test User'
    };

    render(<UserCard user={user} />);

    expect(screen.getByText('Test User')).toBeInTheDocument();
    expect(screen.getByText('test@example.com')).toBeInTheDocument();
    expect(screen.getByText('USER')).toBeInTheDocument();
  });

  it('renders "No name" when name is null', () => {
    const user = {
      id: 1,
      email: 'test@example.com',
      role: 'USER',
      name: null
    };

    render(<UserCard user={user} />);

    expect(screen.getByText('No name')).toBeInTheDocument();
  });
});
```

### Component Integration Tests

Test user interactions:

**Example: admin/src/pages/LoginPage.test.tsx**

```typescript
import { describe, it, expect, vi } from 'vitest';
import { render, screen, waitFor } from '@testing-library/react';
import userEvent from '@testing-library/user-event';
import { LoginPage } from './LoginPage';
import { BrowserRouter } from 'react-router-dom';
import * as api from '../lib/api';

// Mock API
vi.mock('../lib/api');

describe('LoginPage', () => {
  it('submits login form with valid credentials', async () => {
    const user = userEvent.setup();
    const mockLogin = vi.spyOn(api, 'login').mockResolvedValue({
      accessToken: 'token',
      refreshToken: 'refresh',
      user: { id: 1, email: 'test@example.com', role: 'USER' }
    });

    render(
      <BrowserRouter>
        <LoginPage />
      </BrowserRouter>
    );

    // Fill form
    await user.type(screen.getByLabelText(/email/i), 'test@example.com');
    await user.type(screen.getByLabelText(/password/i), 'Password123!');

    // Submit
    await user.click(screen.getByRole('button', { name: /login/i }));

    // Verify API called
    await waitFor(() => {
      expect(mockLogin).toHaveBeenCalledWith({
        email: 'test@example.com',
        password: 'Password123!'
      });
    });
  });

  it('shows error for invalid credentials', async () => {
    const user = userEvent.setup();
    vi.spyOn(api, 'login').mockRejectedValue(
      new Error('Invalid credentials')
    );

    render(
      <BrowserRouter>
        <LoginPage />
      </BrowserRouter>
    );

    await user.type(screen.getByLabelText(/email/i), 'test@example.com');
    await user.type(screen.getByLabelText(/password/i), 'wrong');
    await user.click(screen.getByRole('button', { name: /login/i }));

    await waitFor(() => {
      expect(screen.getByText(/invalid credentials/i)).toBeInTheDocument();
    });
  });

  it('disables submit button while loading', async () => {
    const user = userEvent.setup();
    vi.spyOn(api, 'login').mockImplementation(
      () => new Promise(resolve => setTimeout(resolve, 1000))
    );

    render(
      <BrowserRouter>
        <LoginPage />
      </BrowserRouter>
    );

    const submitButton = screen.getByRole('button', { name: /login/i });

    await user.type(screen.getByLabelText(/email/i), 'test@example.com');
    await user.type(screen.getByLabelText(/password/i), 'Password123!');
    await user.click(submitButton);

    expect(submitButton).toBeDisabled();
  });
});
```

### Testing Hooks

Test custom React hooks:

**Example: admin/src/hooks/useDebounce.test.ts**

```typescript
import { describe, it, expect, vi } from 'vitest';
import { renderHook, waitFor } from '@testing-library/react';
import { useDebounce } from './useDebounce';

describe('useDebounce', () => {
  it('debounces value changes', async () => {
    const { result, rerender } = renderHook(
      ({ value, delay }) => useDebounce(value, delay),
      { initialProps: { value: 'initial', delay: 500 } }
    );

    expect(result.current).toBe('initial');

    // Change value
    rerender({ value: 'updated', delay: 500 });

    // Value should not change immediately
    expect(result.current).toBe('initial');

    // Wait for debounce
    await waitFor(() => {
      expect(result.current).toBe('updated');
    }, { timeout: 600 });
  });
});
```

### Testing Zustand Stores

Test state management:

**Example: admin/src/stores/auth.store.test.ts**

```typescript
import { describe, it, expect, beforeEach } from 'vitest';
import { renderHook, act } from '@testing-library/react';
import { useAuthStore } from './auth.store';

describe('Auth Store', () => {
  beforeEach(() => {
    // Reset store before each test
    const { result } = renderHook(() => useAuthStore());
    act(() => {
      result.current.logout();
    });
  });

  it('sets user on login', () => {
    const { result } = renderHook(() => useAuthStore());

    act(() => {
      result.current.setUser({
        id: 1,
        email: 'test@example.com',
        role: 'USER'
      });
    });

    expect(result.current.user).toEqual({
      id: 1,
      email: 'test@example.com',
      role: 'USER'
    });
    expect(result.current.isAuthenticated).toBe(true);
  });

  it('clears user on logout', () => {
    const { result } = renderHook(() => useAuthStore());

    act(() => {
      result.current.setUser({
        id: 1,
        email: 'test@example.com',
        role: 'USER'
      });
    });

    expect(result.current.isAuthenticated).toBe(true);

    act(() => {
      result.current.logout();
    });

    expect(result.current.user).toBeNull();
    expect(result.current.isAuthenticated).toBe(false);
  });
});
```

## Running Tests

### Run All Tests

```bash
# API tests
cd api
npm test

# Frontend tests
cd admin
npm test
```

### Watch Mode

Run tests automatically on file changes:

```bash
# API tests (Jest watch)
cd api
npm run test:watch

# Frontend tests (Vitest watch)
cd admin
npm run test:watch
```

### Run Specific Tests

```bash
# Run specific test file
npm test -- auth.service.test.ts

# Run tests matching pattern
npm test -- --testNamePattern="login"

# Run tests in specific directory
npm test -- src/modules/auth/
```

### Coverage Reports

Generate test coverage:

```bash
# API coverage
cd api
npm run test:coverage

# Frontend coverage
cd admin
npm run test:coverage
```

**Coverage output:**
```
File                | % Stmts | % Branch | % Funcs | % Lines |
--------------------|---------|----------|---------|---------|
All files           |   82.45 |    75.33 |   80.12 |   83.21 |
 auth/              |   95.23 |    89.47 |   93.75 |   96.15 |
  auth.service.ts   |   97.14 |    91.67 |   100   |   98.21 |
  auth.routes.ts    |   93.33 |    87.50 |   87.50 |   94.12 |
```

**HTML report:**
- Located in `coverage/` directory
- Open `coverage/index.html` in browser
- Shows line-by-line coverage

### CI/CD Testing

**GitHub Actions Example:**

```yaml
name: Tests

on: [push, pull_request]

jobs:
  api-tests:
    runs-on: ubuntu-latest
    services:
      postgres:
        image: postgres:16
        env:
          POSTGRES_PASSWORD: test
        options: >-
          --health-cmd pg_isready
          --health-interval 10s
          --health-timeout 5s
          --health-retries 5

    steps:
      - uses: actions/checkout@v3
      - uses: actions/setup-node@v3
        with:
          node-version: '20'

      - name: Install dependencies
        working-directory: ./api
        run: npm ci

      - name: Run migrations
        working-directory: ./api
        env:
          DATABASE_URL: postgresql://postgres:test@localhost:5432/test
        run: npx prisma migrate deploy

      - name: Run tests
        working-directory: ./api
        run: npm test -- --coverage

      - name: Upload coverage
        uses: codecov/codecov-action@v3
        with:
          files: ./api/coverage/coverage-final.json

  frontend-tests:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v3
      - uses: actions/setup-node@v3
        with:
          node-version: '20'

      - name: Install dependencies
        working-directory: ./admin
        run: npm ci

      - name: Run tests
        working-directory: ./admin
        run: npm test -- --coverage

      - name: Upload coverage
        uses: codecov/codecov-action@v3
        with:
          files: ./admin/coverage/coverage-final.json
```

## Mocking

### Mocking API Calls (Frontend)

```typescript
// Mock axios
vi.mock('../lib/api', () => ({
  api: {
    get: vi.fn(),
    post: vi.fn(),
    put: vi.fn(),
    delete: vi.fn()
  }
}));

// Use in test
import { api } from '../lib/api';

vi.mocked(api.get).mockResolvedValue({
  data: { users: [] }
});
```

### Mocking Database (Backend)

```typescript
// Mock Prisma Client
vi.mock('@prisma/client', () => ({
  PrismaClient: vi.fn(() => ({
    user: {
      findUnique: vi.fn(),
      findMany: vi.fn(),
      create: vi.fn(),
      update: vi.fn(),
      delete: vi.fn()
    }
  }))
}));
```

### Mocking External Services

```typescript
// Mock email service
vi.mock('../../services/email.service', () => ({
  EmailService: {
    sendEmail: vi.fn().mockResolvedValue(true)
  }
}));
```

### Mocking Environment Variables

```typescript
// Set env var for test
process.env.JWT_ACCESS_SECRET = 'test-secret';

// Or use vi.stubEnv
vi.stubEnv('API_URL', 'http://localhost:4000');
```

## Best Practices

### Test Naming

Use descriptive test names:

**Good:**
```typescript
it('should return 401 for expired token', async () => {});
it('should create user with hashed password', async () => {});
it('should render error message for invalid email', () => {});
```

**Bad:**
```typescript
it('works', async () => {});
it('test login', async () => {});
it('should work correctly', () => {});
```

### Test Organization

Group related tests:

```typescript
describe('AuthService', () => {
  describe('login', () => {
    it('should return tokens for valid credentials', () => {});
    it('should throw error for invalid password', () => {});
    it('should throw error for non-existent user', () => {});
  });

  describe('register', () => {
    it('should create new user', () => {});
    it('should hash password', () => {});
    it('should throw error if user exists', () => {});
  });
});
```

### Setup and Teardown

Use beforeEach/afterEach for common setup:

```typescript
describe('UserService', () => {
  let userService: UserService;
  let mockPrisma: any;

  beforeEach(() => {
    mockPrisma = createMockPrisma();
    userService = new UserService(mockPrisma);
  });

  afterEach(() => {
    vi.clearAllMocks();
  });

  it('...', () => {});
});
```

### Avoid Test Interdependence

Each test should be independent:

**Good:**
```typescript
it('should create user', async () => {
  const user = await createUser({ email: 'test@example.com' });
  expect(user.email).toBe('test@example.com');
});

it('should update user', async () => {
  const user = await createUser({ email: 'test@example.com' });
  const updated = await updateUser(user.id, { name: 'New Name' });
  expect(updated.name).toBe('New Name');
});
```

**Bad:**
```typescript
let userId;

it('should create user', async () => {
  const user = await createUser({ email: 'test@example.com' });
  userId = user.id; // ❌ Shared state
});

it('should update user', async () => {
  const updated = await updateUser(userId, { name: 'New Name' });
  // ❌ Depends on previous test
});
```

### Test Edge Cases

Test boundary conditions:

```typescript
describe('pagination', () => {
  it('should handle page 1', () => {});
  it('should handle last page', () => {});
  it('should handle empty results', () => {});
  it('should handle invalid page number', () => {});
  it('should handle page exceeding total', () => {});
});
```

### Async Testing

Always use async/await for async tests:

**Good:**
```typescript
it('should fetch users', async () => {
  const users = await userService.getUsers();
  expect(users).toHaveLength(10);
});
```

**Bad:**
```typescript
it('should fetch users', () => {
  userService.getUsers().then(users => {
    expect(users).toHaveLength(10); // ❌ May not run
  });
});
```

## Coverage Requirements

Target coverage thresholds:

```javascript
// jest.config.js / vitest.config.ts
coverageThreshold: {
  global: {
    branches: 80,
    functions: 80,
    lines: 80,
    statements: 80
  }
}
```

**What to test:**
- ✅ Business logic (services)
- ✅ API routes
- ✅ UI components
- ✅ Custom hooks
- ✅ Utilities
- ❌ Type definitions
- ❌ Config files
- ❌ Test files themselves

## Troubleshooting

### Tests Timing Out

**Problem:** Tests exceed timeout.

**Solution:**

```typescript
// Increase timeout for specific test
it('slow operation', async () => {
  // ...
}, 10000); // 10 second timeout

// Or globally (vitest.config.ts)
export default defineConfig({
  test: {
    testTimeout: 10000
  }
});
```

### Mocks Not Working

**Problem:** Mocks not being used.

**Solution:**

```typescript
// Mock must be at top of file, before imports
vi.mock('../lib/api');

import { api } from '../lib/api';

// Verify mock is being used
console.log(vi.isMockFunction(api.get)); // Should be true
```

### Database Connection Errors

**Problem:** Tests fail with DB connection errors.

**Solution:**

```typescript
// Use separate test database
process.env.DATABASE_URL = 'postgresql://localhost/test_db';

// Or mock database entirely
vi.mock('@prisma/client');
```

### React Testing Library Queries Failing

**Problem:** `screen.getByText()` doesn't find element.

**Solution:**

```typescript
// Use findBy for async elements
const element = await screen.findByText('Loading...');

// Use queryBy to check non-existence
expect(screen.queryByText('Error')).not.toBeInTheDocument();

// Debug rendered output
screen.debug();
```

## Related Documentation

- **Setup:** [Local Development Setup](local-setup.md)
- **Code Style:** [Code Style Guide](code-style.md)
- **TypeScript:** [TypeScript Guide](typescript.md)
- **Debugging:** [Debugging Guide](debugging.md)
- **CI/CD:** [Deployment Guide](../deployment/production.md)

## Summary

You now know:
- ✅ Testing philosophy (test pyramid, AAA pattern)
- ✅ Test frameworks (Jest, Vitest, React Testing Library)
- ✅ How to write unit tests (services, components)
- ✅ How to write integration tests (routes, user flows)
- ✅ How to run tests and generate coverage
- ✅ How to mock dependencies
- ✅ Testing best practices
- ✅ How to integrate tests in CI/CD

**Quick Start:**
```bash
# Install dependencies (when Phase 15 complete)
cd api && npm install --save-dev jest @types/jest ts-jest
cd admin && npm install --save-dev vitest @vitest/ui

# Run tests
npm test

# Watch mode
npm run test:watch

# Coverage
npm run test:coverage
```