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Hexagonal Software Architecture for Web Applications

Testing a Persistence Adapter with Integration Tests

Explore how to effectively test persistence adapters with integration tests in Hexagonal Architecture. Understand why real database interactions are crucial, how to use Spring's @DataJpaTest, and the benefits of running tests against actual databases rather than mocks or in-memory systems.

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As we did for the web controller, it makes sense to cover persistence adapters with integration tests instead of unit tests since we not only want to verify the logic within the adapter, but also the mapping into the database.

Account persistence adapter test

We want to test the persistence adapter we built in the chapter “Implementing a Persistence Adapter”. The adapter has two methods, one for loading an Account entity from the database and another to save new account activities to the database:

Java
@DataJpaTest
@Import({AccountPersistenceAdapter.class, AccountMapper.class})
class AccountPersistenceAdapterTest {
  @Autowired
  private AccountPersistenceAdapter adapter;
  
  @Autowired
  private ActivityRepository activityRepository;
  @Test
  @Sql("AccountPersistenceAdapterTest.sql")
  void loadsAccount() {
    Account account = adapter.loadAccount(
        new AccountId(1L), 
        LocalDateTime.of(2018, 8, 10, 0, 0));
    assertThat(account.getActivityWindow().getActivities()).hasSize(2);
    assertThat(account.calculateBalance()).isEqualTo(Money.of(500));
  }
  
  @Test
  void updatesActivities() {
    Account account = defaultAccount()
        .withBaselineBalance(Money.of(555L))
        .withActivityWindow(new ActivityWindow(
            defaultActivity()
                .withId(null)
                .withMoney(Money.of(1L)).build()))
        .build();
  
    adapter.updateActivities(account);
  
    assertThat(activityRepository.count()).isEqualTo(1);
  
    ActivityJpaEntity savedActivity = activityRepository.findAll().get(0);
    assertThat(savedActivity.getAmount()).isEqualTo(1L);
  }
}

The @DataJpaTest annotation

With @DataJpaTest, we’re telling Spring ...