README.md

Testing Documentation

This directory contains unit tests for the Library Management REST API project.

Test Structure

tests/
├── setup.ts              # Jest setup file
├── helpers/
│   └── mocks.ts          # Shared test helpers (mock Request/Response/session)
├── unit/
│   ├── controllers/      # Controller unit tests
│   ├── middlewares/      # Middleware unit tests
│   ├── routes/           # Route registration tests
│   ├── services/         # Service unit tests
│   └── utils/            # Unit tests for src/utils/ (e.g. errors)
└── README.md             # This file

Running Tests

Run all tests

npm test
# or
pnpm test

Run tests in watch mode

npm run test:watch
# or
pnpm test:watch

Run tests with coverage

npm test -- --coverage
# or
pnpm test -- --coverage

Run a specific test file

npm test -- tests/unit/utils/errors.test.ts

Test Coverage

The project uses Jest for testing with the following coverage goals:

• Statements: > 80%
• Branches: > 80%
• Functions: > 80%
• Lines: > 80%

Coverage reports are generated in the coverage/ directory.

Writing Tests

Test File Naming

• Test files should be named *.test.ts or *.spec.ts
• Place test files next to the source files or in the tests/ directory

Test Structure

describe('ComponentName', () => {
  beforeEach(() => {
    // Setup code
  });

  describe('methodName', () => {
    it('should do something', () => {
      // Test implementation
    });
  });
});

Using Mocks

Common mocks are in tests/helpers/mocks.ts:

• createMockRequest() - Creates a mock Express Request
• createMockResponse() - Creates a mock Express Response
• createMockNext() - Creates a mock NextFunction
• createMockSession() - Creates a mock session with user data

Example Test

import { createMockRequest, createMockResponse, createMockNext } from '../helpers/mocks';

describe('MyMiddleware', () => {
  it('should handle request correctly', () => {
    const req = createMockRequest();
    const res = createMockResponse();
    const next = createMockNext();
    
    // Test implementation
  });
});

Current Test Coverage

Unit Tests

• ✅ Error classes (src/utils/errors.ts)
• ✅ Auth middleware (src/middlewares/auth.ts)
• ✅ Validation middleware (src/middlewares/validation.ts)
• ✅ Auth controller (src/controllers/auth.controller.ts)

Future Tests

• Integration tests for routes
• Service layer tests
• Database operation tests

Best Practices

1. Isolation: Each test should be independent and not rely on other tests
2. Mocking: Mock external dependencies (database, APIs, etc.)
3. Clear Names: Use descriptive test names that explain what is being tested
4. Arrange-Act-Assert: Structure tests with clear setup, execution, and verification
5. Coverage: Aim for high coverage but focus on testing critical paths

Troubleshooting

Jest dependency errors

If you encounter errors like "Cannot find module '@jest/test-sequencer'", try:

pnpm install
# or
npm install

Tests fail with module resolution errors

• Ensure tsconfig.json includes the test files
• Check that jest.config.js has correct moduleNameMapper settings

Mock not working

• Ensure mocks are imported before the module being tested
• Check that jest.mock() is called at the top level of the test file

Type errors in tests

• Ensure @types/jest is installed
• Check that tsconfig.json includes "jest" in the types array