Best-Practices

Laravel remains one of the most popular PHP frameworks. Here are modern development practices for building scalable Laravel applications. 1. Project Structure Recommended Structure app/ ├── Http/ │ ├── Controllers/ │ ├── Middleware/ │ ├── Requests/ │ └── Resources/ ├── Models/ ├── Services/ ├── Repositories/ ├── Events/ ├── Listeners/ └── Jobs/ 2. Eloquent Best Practices Model Relationships // User Model class User extends Model { public function posts() { return $this->hasMany(Post::class); } public function profile() { return $this->hasOne(Profile::class); } public function roles() { return $this->belongsToMany(Role::class); } } Eager Loading // Bad: N+1 problem $users = User::all(); foreach ($users as $user) { echo $user->posts->count(); // Query for each user } // Good: Eager loading $users = User::with('posts')->get(); foreach ($users as $user) { echo $user->posts->count(); // No additional queries } Query Scopes class Post extends Model { public function scopePublished($query) { return $query->where('status', 'published'); } public function scopeRecent($query) { return $query->orderBy('created_at', 'desc'); } } // Usage $posts = Post::published()->recent()->get(); 3. Service Layer Pattern Service Class class UserService { protected $userRepository; protected $emailService; public function __construct( UserRepository $userRepository, EmailService $emailService ) { $this->userRepository = $userRepository; $this->emailService = $emailService; } public function createUser(array $data): User { DB::beginTransaction(); try { $user = $this->userRepository->create($data); $this->emailService->sendWelcomeEmail($user); DB::commit(); return $user; } catch (\Exception $e) { DB::rollBack(); throw $e; } } } 4. Form Requests Validation class CreateUserRequest extends FormRequest { public function rules(): array { return [ 'name' => ['required', 'string', 'max:255'], 'email' => ['required', 'email', 'unique:users,email'], 'password' => ['required', 'string', 'min:8', 'confirmed'], ]; } public function messages(): array { return [ 'email.unique' => 'This email is already registered.', 'password.min' => 'Password must be at least 8 characters.', ]; } } // Controller public function store(CreateUserRequest $request) { $user = $this->userService->createUser($request->validated()); return new UserResource($user); } 5. API Resources Resource Transformation class UserResource extends JsonResource { public function toArray($request): array { return [ 'id' => $this->id, 'name' => $this->name, 'email' => $this->email, 'created_at' => $this->created_at->toIso8601String(), 'posts' => PostResource::collection($this->whenLoaded('posts')), ]; } } 6. Queues and Jobs Job Implementation class SendWelcomeEmail implements ShouldQueue { use Dispatchable, InteractsWithQueue, Queueable, SerializesModels; public function __construct( public User $user ) {} public function handle(EmailService $emailService): void { $emailService->sendWelcomeEmail($this->user); } public function failed(\Throwable $exception): void { // Handle failure } } // Dispatch SendWelcomeEmail::dispatch($user); 7. Events and Listeners Event System // Event class UserRegistered { public function __construct( public User $user ) {} } // Listener class SendWelcomeEmail { public function handle(UserRegistered $event): void { Mail::to($event->user->email)->send(new WelcomeMail($event->user)); } } // Dispatch event(new UserRegistered($user)); 8. Caching Cache Implementation // Cache user $user = Cache::remember("user.{$id}", 3600, function () use ($id) { return User::find($id); }); // Cache tags Cache::tags(['users', 'posts'])->put("user.{$id}", $user, 3600); // Clear cache Cache::tags(['users'])->flush(); 9. Database Migrations Migration Best Practices Schema::create('users', function (Blueprint $table) { $table->id(); $table->string('email')->unique(); $table->string('name'); $table->timestamp('email_verified_at')->nullable(); $table->string('password'); $table->timestamps(); $table->softDeletes(); $table->index('email'); }); 10. Testing Feature Tests class UserTest extends TestCase { use RefreshDatabase; public function test_can_create_user(): void { $response = $this->postJson('/api/users', [ 'name' => 'John Doe', 'email' => '[email protected]', 'password' => 'password123', 'password_confirmation' => 'password123', ]); $response->assertStatus(201) ->assertJsonStructure([ 'data' => [ 'id', 'name', 'email', ] ]); $this->assertDatabaseHas('users', [ 'email' => '[email protected]', ]); } } Best Practices Use Service Layer for business logic Form Requests for validation API Resources for data transformation Queues for long-running tasks Events for decoupled actions Eager Loading to avoid N+1 queries Caching for performance Write Tests for critical paths Conclusion Laravel provides powerful tools for building modern applications. Follow these practices to create maintainable, scalable Laravel applications! 🚀

Spring Boot is the most popular Java framework for building enterprise applications. Here are best practices for building production-ready Spring Boot applications. 1. Project Structure Recommended Structure src/ ├── main/ │ ├── java/ │ │ └── com/example/ │ │ ├── Application.java │ │ ├── config/ │ │ ├── controller/ │ │ ├── service/ │ │ ├── repository/ │ │ ├── model/ │ │ └── dto/ │ └── resources/ │ ├── application.yml │ └── application-prod.yml └── test/ 2. Configuration Management Use YAML for Configuration # application.yml spring: datasource: url: jdbc:postgresql://localhost:5432/mydb username: ${DB_USERNAME} password: ${DB_PASSWORD} jpa: hibernate: ddl-auto: validate show-sql: false properties: hibernate: format_sql: true server: port: 8080 error: include-message: always include-stacktrace: on_param Profile-Based Configuration # application-dev.yml spring: datasource: url: jdbc:h2:mem:testdb jpa: show-sql: true # application-prod.yml spring: datasource: url: ${DATABASE_URL} jpa: show-sql: false 3. Dependency Injection Constructor Injection // Good: Constructor injection @Service public class UserService { private final UserRepository userRepository; private final EmailService emailService; public UserService(UserRepository userRepository, EmailService emailService) { this.userRepository = userRepository; this.emailService = emailService; } } // Bad: Field injection @Service public class UserService { @Autowired private UserRepository userRepository; } 4. Exception Handling Global Exception Handler @RestControllerAdvice public class GlobalExceptionHandler { @ExceptionHandler(ResourceNotFoundException.class) public ResponseEntity<ErrorResponse> handleNotFound( ResourceNotFoundException ex) { ErrorResponse error = new ErrorResponse( HttpStatus.NOT_FOUND.value(), ex.getMessage() ); return ResponseEntity.status(HttpStatus.NOT_FOUND).body(error); } @ExceptionHandler(MethodArgumentNotValidException.class) public ResponseEntity<ErrorResponse> handleValidation( MethodArgumentNotValidException ex) { Map<String, String> errors = new HashMap<>(); ex.getBindingResult().getFieldErrors().forEach(error -> errors.put(error.getField(), error.getDefaultMessage()) ); ErrorResponse error = new ErrorResponse( HttpStatus.BAD_REQUEST.value(), "Validation failed", errors ); return ResponseEntity.badRequest().body(error); } } 5. REST API Design Controller Best Practices @RestController @RequestMapping("/api/v1/users") @Validated public class UserController { private final UserService userService; @GetMapping public ResponseEntity<List<UserDTO>> getAllUsers( @RequestParam(defaultValue = "0") int page, @RequestParam(defaultValue = "20") int size) { List<UserDTO> users = userService.getAllUsers(page, size); return ResponseEntity.ok(users); } @GetMapping("/{id}") public ResponseEntity<UserDTO> getUser(@PathVariable Long id) { UserDTO user = userService.getUserById(id); return ResponseEntity.ok(user); } @PostMapping public ResponseEntity<UserDTO> createUser( @Valid @RequestBody CreateUserRequest request) { UserDTO user = userService.createUser(request); return ResponseEntity.status(HttpStatus.CREATED).body(user); } @PutMapping("/{id}") public ResponseEntity<UserDTO> updateUser( @PathVariable Long id, @Valid @RequestBody UpdateUserRequest request) { UserDTO user = userService.updateUser(id, request); return ResponseEntity.ok(user); } @DeleteMapping("/{id}") public ResponseEntity<Void> deleteUser(@PathVariable Long id) { userService.deleteUser(id); return ResponseEntity.noContent().build(); } } 6. Service Layer Service Implementation @Service @Transactional public class UserService { private final UserRepository userRepository; private final UserMapper userMapper; public UserDTO getUserById(Long id) { User user = userRepository.findById(id) .orElseThrow(() -> new ResourceNotFoundException( "User not found with id: " + id)); return userMapper.toDTO(user); } public UserDTO createUser(CreateUserRequest request) { if (userRepository.existsByEmail(request.getEmail())) { throw new DuplicateResourceException( "Email already exists"); } User user = userMapper.toEntity(request); user = userRepository.save(user); return userMapper.toDTO(user); } } 7. Repository Layer JPA Repository @Repository public interface UserRepository extends JpaRepository<User, Long> { Optional<User> findByEmail(String email); boolean existsByEmail(String email); @Query("SELECT u FROM User u WHERE u.status = :status") List<User> findByStatus(@Param("status") UserStatus status); @Modifying @Query("UPDATE User u SET u.status = :status WHERE u.id = :id") int updateStatus(@Param("id") Long id, @Param("status") UserStatus status); } 8. Entity Design JPA Entity @Entity @Table(name = "users") public class User { @Id @GeneratedValue(strategy = GenerationType.IDENTITY) private Long id; @Column(nullable = false, unique = true) private String email; @Column(nullable = false) private String name; @Enumerated(EnumType.STRING) private UserStatus status; @CreatedDate private LocalDateTime createdAt; @LastModifiedDate private LocalDateTime updatedAt; @Version private Long version; // Getters and setters } 9. Validation DTO Validation public class CreateUserRequest { @NotBlank(message = "Email is required") @Email(message = "Invalid email format") private String email; @NotBlank(message = "Name is required") @Size(min = 2, max = 100, message = "Name must be between 2 and 100 characters") private String name; @Min(value = 18, message = "Age must be at least 18") @Max(value = 120, message = "Age must be at most 120") private Integer age; // Getters and setters } 10. Security Spring Security Configuration @Configuration @EnableWebSecurity public class SecurityConfig { @Bean public SecurityFilterChain filterChain(HttpSecurity http) throws Exception { http .csrf().disable() .authorizeHttpRequests(auth -> auth .requestMatchers("/api/public/**").permitAll() .requestMatchers("/api/admin/**").hasRole("ADMIN") .anyRequest().authenticated() ) .sessionManagement(session -> session .sessionCreationPolicy(SessionCreationPolicy.STATELESS) ) .oauth2ResourceServer(oauth2 -> oauth2 .jwt(jwt -> jwt.decoder(jwtDecoder())) ); return http.build(); } } 11. Testing Unit Tests @ExtendWith(MockitoExtension.class) class UserServiceTest { @Mock private UserRepository userRepository; @InjectMocks private UserService userService; @Test void shouldCreateUser() { // Given CreateUserRequest request = new CreateUserRequest(); request.setEmail("[email protected]"); request.setName("Test User"); User savedUser = new User(); savedUser.setId(1L); savedUser.setEmail(request.getEmail()); when(userRepository.existsByEmail(request.getEmail())).thenReturn(false); when(userRepository.save(any(User.class))).thenReturn(savedUser); // When UserDTO result = userService.createUser(request); // Then assertThat(result.getId()).isEqualTo(1L); assertThat(result.getEmail()).isEqualTo("[email protected]"); } } Integration Tests @SpringBootTest @AutoConfigureMockMvc class UserControllerIntegrationTest { @Autowired private MockMvc mockMvc; @Autowired private UserRepository userRepository; @Test void shouldCreateUser() throws Exception { CreateUserRequest request = new CreateUserRequest(); request.setEmail("[email protected]"); request.setName("Test User"); mockMvc.perform(post("/api/v1/users") .contentType(MediaType.APPLICATION_JSON) .content(objectMapper.writeValueAsString(request))) .andExpect(status().isCreated()) .andExpect(jsonPath("$.email").value("[email protected]")); } } 12. Performance Optimization Connection Pooling spring: datasource: hikari: maximum-pool-size: 20 minimum-idle: 5 connection-timeout: 30000 idle-timeout: 600000 max-lifetime: 1800000 Caching @Configuration @EnableCaching public class CacheConfig { @Bean public CacheManager cacheManager() { return new ConcurrentMapCacheManager("users", "posts"); } } // Usage @Service public class UserService { @Cacheable(value = "users", key = "#id") public UserDTO getUserById(Long id) { return userRepository.findById(id) .map(userMapper::toDTO) .orElseThrow(); } @CacheEvict(value = "users", key = "#id") public void deleteUser(Long id) { userRepository.deleteById(id); } } 13. Monitoring and Logging Actuator Endpoints management: endpoints: web: exposure: include: health,info,metrics,prometheus endpoint: health: show-details: when-authorized Logging Configuration logging: level: root: INFO com.example: DEBUG pattern: console: "%d{yyyy-MM-dd HH:mm:ss} - %msg%n" file: "%d{yyyy-MM-dd HH:mm:ss} [%thread] %-5level %logger{36} - %msg%n" file: name: logs/application.log max-size: 10MB max-history: 30 Best Practices Summary Use constructor injection for dependencies Implement global exception handling Validate all inputs with Bean Validation Use DTOs to separate API from domain models Implement proper logging and monitoring Use profiles for environment-specific config Write comprehensive tests Optimize database queries Implement caching where appropriate Follow RESTful conventions Conclusion Spring Boot best practices help you build: ...

Good API design is crucial for developer experience and system success. Here are best practices for designing RESTful APIs. 1. Use RESTful Conventions Resource-Based URLs # Good: Resource-based GET /api/users GET /api/users/123 POST /api/users PUT /api/users/123 DELETE /api/users/123 # Bad: Action-based GET /api/getUsers POST /api/createUser POST /api/deleteUser HTTP Methods GET: Retrieve resources POST: Create resources PUT: Update entire resource PATCH: Partial update DELETE: Remove resource 2. Consistent Naming Use Plural Nouns # Good GET /api/users GET /api/orders GET /api/products # Bad GET /api/user GET /api/order GET /api/product Use kebab-case or camelCase # Good: Consistent GET /api/user-profiles GET /api/orderItems # Bad: Mixed GET /api/user_profiles GET /api/order-items 3. Version Your API URL Versioning GET /api/v1/users GET /api/v2/users Header Versioning GET /api/users Accept: application/vnd.api+json;version=2 4. Use Proper HTTP Status Codes Success Codes 200 OK # Successful GET, PUT, PATCH 201 Created # Successful POST 204 No Content # Successful DELETE Client Error Codes 400 Bad Request # Invalid request 401 Unauthorized # Authentication required 403 Forbidden # Not authorized 404 Not Found # Resource doesn't exist 409 Conflict # Resource conflict 422 Unprocessable # Validation errors Server Error Codes 500 Internal Server Error 502 Bad Gateway 503 Service Unavailable 5. Consistent Response Format Standard Response Structure { "data": { "id": "123", "type": "user", "attributes": { "name": "John Doe", "email": "[email protected]" } }, "meta": { "timestamp": "2025-12-10T10:00:00Z" } } Error Response Format { "error": { "code": "VALIDATION_ERROR", "message": "Invalid input", "details": [ { "field": "email", "message": "Invalid email format" } ] } } 6. Pagination Cursor-Based Pagination GET /api/users?cursor=eyJpZCI6IjEyMyJ9&limit=20 Response: { "data": [...], "pagination": { "cursor": "eyJpZCI6IjE0MyJ9", "has_more": true } } Offset-Based Pagination GET /api/users?page=1&limit=20 Response: { "data": [...], "pagination": { "page": 1, "limit": 20, "total": 100, "total_pages": 5 } } 7. Filtering and Sorting Filtering GET /api/users?status=active&role=admin GET /api/orders?created_after=2024-01-01&created_before=2024-12-31 Sorting GET /api/users?sort=name,email&order=asc,desc GET /api/users?sort=-created_at # Descending 8. Field Selection Sparse Fieldsets GET /api/users?fields=id,name,email GET /api/users/123?fields=id,name Include Related Resources GET /api/users/123?include=orders,profile 9. Rate Limiting Headers X-RateLimit-Limit: 1000 X-RateLimit-Remaining: 999 X-RateLimit-Reset: 1609459200 Response HTTP/1.1 429 Too Many Requests Retry-After: 60 10. Authentication and Authorization Use Standard Methods # Bearer token Authorization: Bearer <token> # API key X-API-Key: <key> Return Clear Errors { "error": { "code": "UNAUTHORIZED", "message": "Invalid or expired token" } } 11. Documentation OpenAPI/Swagger openapi: 3.0.0 info: title: User API version: 1.0.0 paths: /users: get: summary: List users responses: '200': description: Success Interactive Documentation Swagger UI: Visual API documentation Postman: API testing and docs Redoc: Beautiful API docs 12. Error Handling Consistent Error Format { "error": { "code": "RESOURCE_NOT_FOUND", "message": "User with ID 123 not found", "request_id": "req_abc123" } } Validation Errors { "error": { "code": "VALIDATION_ERROR", "message": "Validation failed", "errors": [ { "field": "email", "message": "Invalid email format", "code": "INVALID_FORMAT" } ] } } 13. Caching Cache Headers Cache-Control: public, max-age=3600 ETag: "33a64df551425fcc55e4d42a148795d9f25f89d4" Last-Modified: Wed, 21 Oct 2015 07:28:00 GMT Conditional Requests GET /api/users/123 If-None-Match: "33a64df551425fcc55e4d42a148795d9f25f89d4" # 304 Not Modified if unchanged 14. Security Best Practices Use HTTPS Always use HTTPS in production. ...

TypeScript has become the de facto standard for large-scale JavaScript applications. Here are the best practices to write better type-safe code in 2025. 1. Use Strict Mode Always enable strict mode in tsconfig.json: { "compilerOptions": { "strict": true, "noImplicitAny": true, "strictNullChecks": true, "strictFunctionTypes": true, "strictBindCallApply": true, "strictPropertyInitialization": true, "noImplicitThis": true, "alwaysStrict": true } } 2. Prefer Interfaces for Object Shapes Use interfaces for object shapes, types for unions/intersections: // Good: Interface for object shape interface User { id: string; name: string; email: string; } // Good: Type for union type Status = 'pending' | 'approved' | 'rejected'; // Good: Type for intersection type AdminUser = User & { role: 'admin' }; 3. Use Discriminated Unions Make type narrowing easier with discriminated unions: ...

Three weeks ago, I had 191,000 tokens in my upcoming tactical survival roguelite game’s codebase. Today, I have 104,000 tokens: a 45% reduction. Here’s what I learned about AI-generated code and why removing it made my game better. The Problem with AI-Generated Code What is “AI Slop”? AI slop refers to code that: Works but is unnecessarily verbose Lacks clear intent and purpose Contains redundant patterns Has inconsistent style Includes unnecessary abstractions Lacks proper error handling Has poor performance characteristics Why Does It Happen? AI tools like ChatGPT and GitHub Copilot: ...

Designing a REST API that is intuitive, maintainable, and scalable requires following established best practices. Here’s a comprehensive guide. 1. Use Nouns, Not Verbs Good GET /users GET /users/123 POST /users PUT /users/123 DELETE /users/123 Bad GET /getUsers GET /getUserById POST /createUser PUT /updateUser DELETE /deleteUser 2. Use Plural Nouns Good GET /users GET /orders GET /products Bad GET /user GET /order GET /product 3. Use HTTP Methods Correctly // GET - Retrieve resources GET /users // Get all users GET /users/123 // Get specific user // POST - Create new resources POST /users // Create new user // PUT - Update entire resource PUT /users/123 // Replace user // PATCH - Partial update PATCH /users/123 // Update specific fields // DELETE - Remove resources DELETE /users/123 // Delete user 4. Use Proper HTTP Status Codes // Success 200 OK // Successful GET, PUT, PATCH 201 Created // Successful POST 204 No Content // Successful DELETE // Client Errors 400 Bad Request // Invalid request 401 Unauthorized // Authentication required 403 Forbidden // Insufficient permissions 404 Not Found // Resource doesn't exist 409 Conflict // Resource conflict // Server Errors 500 Internal Server Error 503 Service Unavailable 5. Consistent Response Format { "data": { "id": 123, "name": "John Doe", "email": "[email protected]" }, "meta": { "timestamp": "2024-11-15T10:00:00Z" } } Error Response Format { "error": { "code": "VALIDATION_ERROR", "message": "Invalid input data", "details": [ { "field": "email", "message": "Invalid email format" } ] } } 6. Versioning URL Versioning /api/v1/users /api/v2/users Header Versioning Accept: application/vnd.api+json;version=1 7. Filtering, Sorting, Pagination GET /users?page=1&limit=20 GET /users?sort=name&order=asc GET /users?status=active&role=admin GET /users?search=john 8. Nested Resources GET /users/123/posts POST /users/123/posts GET /users/123/posts/456 PUT /users/123/posts/456 DELETE /users/123/posts/456 9. Use HTTPS Always use HTTPS in production to encrypt data in transit. ...

Security is crucial in web development. Here are essential security practices to protect your applications. 1. Authentication & Authorization Strong Password Policies // Enforce strong passwords const passwordRegex = /^(?=.*[a-z])(?=.*[A-Z])(?=.*\d)(?=.*[@$!%*?&])[A-Za-z\d@$!%*?&]{8,}$/; // Hash passwords (never store plaintext) const hashedPassword = await bcrypt.hash(password, 10); JWT Best Practices // Use short expiration times const token = jwt.sign( { userId: user.id }, process.env.JWT_SECRET, { expiresIn: '15m' } ); // Implement refresh tokens // Store tokens securely (httpOnly cookies) 2. Input Validation Server-Side Validation // Always validate on server const schema = z.object({ email: z.string().email(), password: z.string().min(8), age: z.number().min(18).max(120) }); const validated = schema.parse(req.body); Sanitize Inputs // Prevent XSS const sanitized = DOMPurify.sanitize(userInput); // Prevent SQL Injection (use parameterized queries) db.query('SELECT * FROM users WHERE id = ?', [userId]); 3. HTTPS & SSL/TLS // Always use HTTPS in production // Redirect HTTP to HTTPS // Use HSTS headers app.use((req, res, next) => { if (!req.secure && process.env.NODE_ENV === 'production') { return res.redirect(`https://${req.headers.host}${req.url}`); } next(); }); 4. CORS Configuration // Configure CORS properly app.use(cors({ origin: process.env.ALLOWED_ORIGINS.split(','), credentials: true, methods: ['GET', 'POST', 'PUT', 'DELETE'], allowedHeaders: ['Content-Type', 'Authorization'] })); 5. Rate Limiting // Prevent brute force attacks const rateLimit = require('express-rate-limit'); const limiter = rateLimit({ windowMs: 15 * 60 * 1000, // 15 minutes max: 5 // limit each IP to 5 requests per windowMs }); app.use('/api/login', limiter); 6. SQL Injection Prevention // Always use parameterized queries // Bad db.query(`SELECT * FROM users WHERE email = '${email}'`); // Good db.query('SELECT * FROM users WHERE email = ?', [email]); 7. XSS Prevention // Escape user input const escapeHtml = (text) => { const map = { '&': '&amp;', '<': '&lt;', '>': '&gt;', '"': '&quot;', "'": '&#039;' }; return text.replace(/[&<>"']/g, m => map[m]); }; // Use Content Security Policy app.use((req, res, next) => { res.setHeader('Content-Security-Policy', "default-src 'self'; script-src 'self'"); next(); }); 8. CSRF Protection // Use CSRF tokens const csrf = require('csurf'); const csrfProtection = csrf({ cookie: true }); app.use(csrfProtection); app.get('/form', (req, res) => { res.render('form', { csrfToken: req.csrfToken() }); }); 9. Security Headers // Set security headers app.use((req, res, next) => { res.setHeader('X-Content-Type-Options', 'nosniff'); res.setHeader('X-Frame-Options', 'DENY'); res.setHeader('X-XSS-Protection', '1; mode=block'); res.setHeader('Strict-Transport-Security', 'max-age=31536000'); next(); }); 10. Dependency Security # Regularly update dependencies npm audit npm audit fix # Use tools like Snyk, Dependabot 11. Error Handling // Don't expose sensitive information app.use((err, req, res, next) => { if (process.env.NODE_ENV === 'production') { res.status(500).json({ error: 'Internal server error' }); } else { res.status(500).json({ error: err.message }); } }); 12. Logging & Monitoring // Log security events logger.warn('Failed login attempt', { ip: req.ip, email: req.body.email, timestamp: new Date() }); // Monitor for suspicious activity Best Practices Summary Strong authentication Input validation & sanitization Use HTTPS Configure CORS properly Implement rate limiting Prevent SQL injection Prevent XSS CSRF protection Security headers Keep dependencies updated Proper error handling Monitor security events Conclusion Security requires: ...

Comprehensive testing is essential for reliable backend systems. Here’s a guide to effective testing strategies. Testing Pyramid /\ / \ E2E Tests (Few) /____\ / \ Integration Tests (Some) /________\ / \ Unit Tests (Many) /____________\ 1. Unit Tests What to Test Individual functions Business logic Data transformations Edge cases Example describe('UserService', () => { it('should create user with valid data', () => { const userData = { email: '[email protected]', name: 'Test User' }; const user = userService.createUser(userData); expect(user.email).toBe('[email protected]'); expect(user.id).toBeDefined(); }); it('should throw error for duplicate email', () => { userService.createUser({ email: '[email protected]' }); expect(() => { userService.createUser({ email: '[email protected]' }); }).toThrow('Email already exists'); }); }); 2. Integration Tests What to Test API endpoints Database operations External service interactions Service integration Example describe('User API', () => { beforeEach(async () => { await db.migrate.latest(); }); afterEach(async () => { await db.migrate.rollback(); }); it('POST /api/users should create user', async () => { const response = await request(app) .post('/api/users') .send({ email: '[email protected]', name: 'Test User', password: 'password123' }) .expect(201); expect(response.body.email).toBe('[email protected]'); const user = await db('users').where({ email: '[email protected]' }).first(); expect(user).toBeDefined(); }); }); 3. End-to-End Tests What to Test Complete user workflows System integration Critical paths Example describe('User Registration Flow', () => { it('should complete full registration process', async () => { // Register user const registerResponse = await request(app) .post('/api/auth/register') .send({ email: '[email protected]', password: 'password123' }); expect(registerResponse.status).toBe(201); // Login const loginResponse = await request(app) .post('/api/auth/login') .send({ email: '[email protected]', password: 'password123' }); expect(loginResponse.status).toBe(200); expect(loginResponse.body.token).toBeDefined(); // Access protected route const profileResponse = await request(app) .get('/api/users/me') .set('Authorization', `Bearer ${loginResponse.body.token}`); expect(profileResponse.status).toBe(200); }); }); 4. Test Data Management Fixtures const userFixtures = { validUser: { email: '[email protected]', name: 'Test User', password: 'password123' }, adminUser: { email: '[email protected]', name: 'Admin', password: 'admin123', role: 'admin' } }; Factories function createUser(overrides = {}) { return { email: '[email protected]', name: 'Test User', password: 'password123', ...overrides }; } 5. Mocking External Services // Mock external API jest.mock('../services/paymentService', () => ({ processPayment: jest.fn().mockResolvedValue({ transactionId: 'tx_123', status: 'success' }) })); 6. Database Testing // Use test database const testDb = { host: process.env.TEST_DB_HOST, database: process.env.TEST_DB_NAME }; // Clean database between tests beforeEach(async () => { await db.raw('TRUNCATE TABLE users CASCADE'); }); 7. Test Coverage // Aim for high coverage // Focus on critical paths // Don't obsess over 100% // Use coverage tools // jest --coverage // nyc Best Practices Write tests first (TDD) Test behavior, not implementation Keep tests independent Use descriptive test names Test edge cases Mock external dependencies Clean up test data Run tests in CI/CD Maintain test code quality Review test failures Conclusion Effective testing requires: ...

Understanding Java class initialization order is crucial for avoiding subtle bugs. Here’s the real initialization sequence and common pitfalls. Initialization Order Static Fields and Blocks public class Example { // 1. Static fields initialized first private static int staticField = initializeStatic(); // 2. Static blocks executed in order static { System.out.println("Static block 1"); } static { System.out.println("Static block 2"); } private static int initializeStatic() { System.out.println("Static field initialization"); return 1; } } Instance Fields and Constructors public class Example { // 3. Instance fields initialized private int instanceField = initializeInstance(); // 4. Instance initialization blocks { System.out.println("Instance block"); } // 5. Constructor executed last public Example() { System.out.println("Constructor"); } private int initializeInstance() { System.out.println("Instance field initialization"); return 1; } } Complete Initialization Sequence public class InitializationDemo { // Step 1: Static fields private static String staticField = "Static field"; // Step 2: Static blocks (in order) static { System.out.println("Static block 1"); } static { System.out.println("Static block 2"); } // Step 3: Instance fields private String instanceField = "Instance field"; // Step 4: Instance blocks { System.out.println("Instance block"); } // Step 5: Constructor public InitializationDemo() { System.out.println("Constructor"); } } Common Pitfalls 1. Forward References // Bad: Forward reference public class BadExample { private int value = getValue(); // Error: forward reference private int multiplier = 10; private int getValue() { return multiplier * 2; // multiplier might not be initialized } } // Good: Initialize in correct order public class GoodExample { private int multiplier = 10; private int value = getValue(); private int getValue() { return multiplier * 2; } } 2. Static vs Instance Initialization public class ConfusingExample { private static int staticCounter = 0; private int instanceCounter = 0; static { staticCounter++; // Cannot access instanceCounter here! } { instanceCounter++; staticCounter++; // Can access static } } 3. Inheritance Initialization class Parent { static { System.out.println("Parent static block"); } { System.out.println("Parent instance block"); } public Parent() { System.out.println("Parent constructor"); } } class Child extends Parent { static { System.out.println("Child static block"); } { System.out.println("Child instance block"); } public Child() { System.out.println("Child constructor"); } } // Output order: // Parent static block // Child static block // Parent instance block // Parent constructor // Child instance block // Child constructor Best Practices Initialize fields in logical order Avoid forward references Keep initialization blocks simple Use constructors for complex initialization Document initialization dependencies Conclusion Understanding initialization order helps you: ...