Testing cache in Spring Data Jpa - unit-testing

Question

I have a code where I am applying caching to get an object.
service:
#Service
class UserServiceImpl(
private val userRepository: UserRepository
) : UserService {
override fun create(userEntity: UserEntity): UserEntity = userRepository.save(userEntity)
.also { log.info("saved user {}", it) }
#Cacheable("users", key = "#id")
override fun get(id: Long): UserEntity = userRepository.findById(id)
.orElseThrow { EntityNotFoundException("User not found by id $id") }
.also { log.info("from db: received user {}", it) }
companion object {
private val log = KotlinLogging.logger { }
}
}
repository:
#Repository
interface UserRepository : JpaRepository<UserEntity, Long> {
}
I have verified with a simple controller that the caching works well, but I cannot verify this with tests. Test fails with an error: Verification failed: call 1 of 1: UserRepository(#1).findById(eq(1))). 3 matching calls found, but needs at least 1 and at most 1 calls
class UserServiceImplTest {
private val userRepository = mockkClass(UserRepository::class)
private val userService: UserService = UserServiceImpl(userRepository)
#Test
fun `get should use caching`() {
// given
val user = UserEntity(1, "Anna", "anna#gmail.com")
every { userRepository.save(user)} returns user
every { userRepository.findById(user.id!!) } returns Optional.of(user)
// when
userService.get(user.id!!)
userService.get(user.id!!)
userService.get(user.id!!)
// then
verify(exactly = 1) { userRepository.findById(user.id!!) }
}
}
Perhaps I need to somehow enable caching for tests too. Or my test is written incorrectly (which is most likely). How can I write a test to check that the caching is working?

Answer 1

#Cacheable will generate a wrapper method which does the caching. This wrapper will exist on the proxy generated by Spring, so it will not come into play when you create the UserServiceImpl yourself. If you want to test it, you need to let Spring context manage the classes, including the mock.
For instance,
#SpringBootTest
class UserServiceImplTest {
#MockBean
lateinit var userRepository: UserRepository
#Autowired
lateinit var userService: UserService
#Test
fun `get should use caching`() {
// given
val user = UserEntity(1, "Anna", "anna#gmail.com")
every { userRepository.save(user)} returns user
every { userRepository.findById(user.id!!) } returns Optional.of(user)
// when
userService.get(user.id!!)
userService.get(user.id!!)
userService.get(user.id!!)
// then
verify(exactly = 1) { userRepository.findById(user.id!!) }
}
}