@MockBean seems to rerun context creation and fails afterMigrate.sql

Question

I have two integration test classes. One of these classes depends on the bean that is talking to external service, so I need to mock this bean, and @MockBean seems perfect for this. For injecting some seeds into DB I'm using flyway's afterMigrate.sql. So here is hot it looks like:

@RunWith(SpringRunner.class)
@ActiveProfiles("test")
@SpringBootTest
@Transactional
@Rollback
class FooTest {

  @Autowired
  private MyService myService;
}

@RunWith(SpringRunner.class)
@ActiveProfiles("test")
@SpringBootTest
@Transactional
@Rollback
class BarTest {

  @MockBean
  private ExternalService;

  @Autowired
  private MyService myService;
}

And afterMigrate.sql:

INSERT INTO my_table (id, name) VALUES (1, 'John Doe')

The problem appeared when I annotate the ExternatService as @MockBean as now the afretMigrate.sql runs twice and I'm getting the error:

java.lang.IllegalStateException: Failed to load ApplicationContext
....
Message    : ERROR: duplicate key value violates unique constraint "my_table_pkey"

When I'm changing the @MockBean to @Autowired the error is gone and context is created without any problems. Also, tests run without problems if I run BarTest separately. This is not the expected behavior for @MockBean as the documentation says:

Any existing single bean of the same type defined in the context will be replaced by the mock. If no existing bean is defined a new one will be added. Dependencies that are known to the application context but are not beans (such as those registered directly) will not be found and a mocked bean will be added to the context alongside the existing dependency.

It does not say that the context will be recreated.

Sergii Bishyr · Accepted Answer · 2019-05-29 09:47:09Z

8

Because when you use @MockBean annotation your context will be loaded for each test. Please refer to this github issue. The citation from this page :

The Spring test framework will cache an ApplicationContext whenever possible between test runs. In order to be cached, the context must have an exactly equivalent configuration. Whenever you use @MockBean, you are by definition changing the context configuration.

So when you use your mock bean in different tests - the context will be recreated each time for your test class. So if you for example have some beans that load data to DB on context creation - for example beans for flyway - they will be created each time context is recreated.

edited May 29, 2019 at 9:47

Sergii Bishyr

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answered May 28, 2019 at 15:58

Michał Krzywański

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Sergii Bishyr · Accepted Answer · 2019-05-29 09:52:00Z

Here is how I have resolved this issue (which I consider an issue).

Solution 1: I have created a MockConfig class with that should create one mock for entire test suite:

@Configration
public class MockConfig {

  @Bean
  @Primary
  public ExternalService externalService() {
    return mock(ExternalService.class);
  }
}

And in the test, I'm just autowiring the external service:

@Autowire
private ExternalService externalService;

But this solution has a problem, it will create a real bean then will override it with the mock bean. If your external service make a connection to the external resources on creation, and you don't need that then you will need another solution.

Solution 2: Create a basic abstract class with @MockBean in it:

@RunWith(SpringRunner.class)
@ActiveProfiles("test")
@SpringBootTest
@Transactional
@Rollback
public abstract class BaseIntegrationTest {
  @MockBean
  ExternalService externalService;
}

And extend the integration test from this base class:

class FooTest extends BaseIntegrationTest {

  @Autowired
  private MyService myService;
}

class BarTest extends BaseIntegrationTest {

  @Autowired
  private MyService myService;
}

Now the context won't refresh as it's always the same, and the real bean won't be created.

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