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Service Testing

Test business logic in service layers with mocked dependencies.

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Service Testing

Service Test Example

@ExtendWith(MockitoExtension.class)
class OrderServiceTest {

    @Mock private OrderRepository repository;
    @Mock private PaymentService paymentService;
    @InjectMocks private OrderService service;

    @Test
    void shouldCreateOrderAndProcessPayment() {
        when(repository.save(any())).thenAnswer(inv -> inv.getArgument(0));
        when(paymentService.charge(any(), anyDouble())).thenReturn(true);

        Order order = service.create(new OrderRequest("laptop", 999.99));

        assertThat(order).isNotNull();
        verify(repository).save(any());
        verify(paymentService).charge(any(), eq(999.99));
    }
}

Testing Strategies

Testing Pyramid

     /  E2E  \
    /----------\
   / Integration \
  /----------------\
 /      Unit        \
/--------------------

Test Types

  • Unit: Individual components
  • Integration: Component interactions
  • E2E: Full user workflows
  • Performance: Load/stress testing

Best Practices

  • Write tests first (TDD)
  • Aim for 80% coverage
  • Test edge cases
  • Keep tests fast and isolated

Key Points

  • Understanding Service Testing is essential for production systems
  • Always consider scalability and maintainability
  • Test thoroughly before deploying to production
  • Monitor performance and set up alerting

Common Patterns

  1. Validation: Always validate input at the boundary
  2. Error Handling: Use structured error responses
  3. Logging: Log key events for debugging
  4. Testing: Unit, integration, and load tests
  5. Documentation: Keep docs updated with code changes

Practice Problems

0/3solved
Implement Service Testing

Design and implement a solution for Service Testing in a backend system. Consider scalability, error handling, and production readiness.

Solution
// Service Testing implementation
// Key aspects: validation, error handling, logging, testing

public class ServiceTesting {
    // Production-ready implementation
}
Service Testing Edge Cases

Identify and handle edge cases for Service Testing. What happens under high load, with invalid input, or during failures?

Solution
// Edge case handling:
// 1. Null/empty input -> validation
// 2. High load -> rate limiting, queuing
// 3. Failures -> retries, circuit breaker
// 4. Concurrent access -> locks, idempotency
Service Testing Testing Strategy

Write a testing strategy for Service Testing. Include unit tests, integration tests, and performance tests.

Solution
// Test plan:
// - Unit: 80% coverage target
// - Integration: API contracts
// - Performance: latency, throughput
// - Chaos: failure injection

Quiz

1. Service testing mocks?

Question 1 options

2. verify() checks?

Question 2 options

3. What is the primary purpose of Service Testing?

Question 3 options

4. What is a common mistake when implementing Service Testing?

Question 4 options

Flashcards

Question

Service testing mocks?

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Answer

Repository and external dependencies

Question

verify() checks?

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Answer

Method was called with expected args

Question

What is Service Testing?

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Answer

Service Testing is a key concept in backend development.

Question

When to use Service Testing?

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Answer

Use Service Testing when building production systems that require reliability, scalability, and maintainability.

Question

Service Testing best practices

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Answer

Follow SOLID principles, write clean code, test thoroughly, document decisions, and monitor in production.

Revision Notes

Key Takeaways

  • 1.Service tests mock repositories and dependencies
  • 2.Verify business logic, not implementation
  • 3.Test success and failure paths
  • 4.Use @InjectMocks and @Mock

Interview Tips

  • •Write service tests
  • •Mock external dependencies

Cheat Sheet

Service Testing

  • Mock: repositories, external services
  • Verify: business logic
  • Test: success + failure paths
  • @InjectMocks + @Mock