Unit Testing Spring Caching

Overview

This skill provides patterns for unit testing Spring caching annotations (@Cacheable, @CacheEvict, @CachePut) without full Spring context. It covers cache hits/misses, invalidation, key generation, and conditional caching using in-memory ConcurrentMapCacheManager.

When to Use

• Writing unit tests for @Cacheable method behavior
• Verifying @CacheEvict cache invalidation works correctly
• Testing @CachePut cache updates
• Validating cache key generation from SpEL expressions
• Testing conditional caching with unless/condition parameters
• Mocking cache managers in fast unit tests without Redis

Instructions

1. Configure in-memory CacheManager: Use ConcurrentMapCacheManager for tests
2. Set up test fixtures: Mock repository and create service instance in @BeforeEach
3. Verify repository call counts: Use times(n) assertions to confirm cache behavior
4. Test cache hit: Call method twice, verify repository called once
5. Test cache miss: Verify repository called on each invocation
6. Test eviction: After @CacheEvict, verify repository called again on next read
7. Test key generation: Verify compound keys from SpEL expressions
8. Validate conditional caching: Test unless (null results) and condition (parameter-based)

Validation checkpoints:

• Run test → If cache not working: verify @EnableCaching annotation present
• If proxy issues: ensure method calls go through Spring proxy (no direct this calls)
• If key mismatches: log actual cache key and compare with @Cacheable(key="...") expression

Examples

Maven

<dependency>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-starter-cache</artifactId>
</dependency>
<dependency>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-starter-test</artifactId>
  <scope>test</scope>
</dependency>

Gradle

dependencies {
  implementation("org.springframework.boot:spring-boot-starter-cache")
  testImplementation("org.springframework.boot:spring-boot-starter-test")
}

Testing @Cacheable (Cache Hit/Miss)

// Service
@Service
public class UserService {
  private final UserRepository userRepository;

  public UserService(UserRepository userRepository) {
    this.userRepository = userRepository;
  }

  @Cacheable("users")
  public User getUserById(Long id) {
    return userRepository.findById(id).orElse(null);
  }
}

// Test
class UserServiceCachingTest {

  private UserRepository userRepository;
  private UserService userService;

  @BeforeEach
  void setUp() {
    userRepository = mock(UserRepository.class);
    userService = new UserService(userRepository);
  }

  @Test
  void shouldCacheUserAfterFirstCall() {
    User user = new User(1L, "Alice");
    when(userRepository.findById(1L)).thenReturn(Optional.of(user));

    // First call - hits database
    User firstCall = userService.getUserById(1L);
    // Second call - hits cache
    User secondCall = userService.getUserById(1L);

    assertThat(firstCall).isEqualTo(secondCall);
    verify(userRepository, times(1)).findById(1L); // Only once due to cache
  }

  @Test
  void shouldInvokeRepositoryOnCacheMiss() {
    when(userRepository.findById(1L)).thenReturn(Optional.of(new User(1L, "Bob")));

    userService.getUserById(1L);
    userService.getUserById(1L);

    verify(userRepository, times(2)).findById(1L); // No caching occurred
  }
}

Testing @CacheEvict

// Service
@Service
public class ProductService {
  private final ProductRepository productRepository;

  public ProductService(ProductRepository productRepository) {
    this.productRepository = productRepository;
  }

  @Cacheable("products")
  public Product getProductById(Long id) {
    return productRepository.findById(id).orElse(null);
  }

  @CacheEvict("products")
  public void deleteProduct(Long id) {
    productRepository.deleteById(id);
  }
}

// Test
class ProductCacheEvictTest {

  private ProductRepository productRepository;
  private ProductService productService;

  @BeforeEach
  void setUp() {
    productRepository = mock(ProductRepository.class);
    productService = new ProductService(productRepository);
  }

  @Test
  void shouldEvictProductFromCacheWhenDeleted() {
    Product product = new Product(1L, "Laptop", 999.99);
    when(productRepository.findById(1L)).thenReturn(Optional.of(product));

    productService.getProductById
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