In this case you need to configure mocks in a way we used to do it before @MockBean was introduced – by specifying manually a @Primary bean that will replace the original one in the context.
@SpringBootTest
class DemoApplicationTests {
@TestConfiguration
public static class TestConfig {
@Bean
@Primary
public SystemTypeDetector mockSystemTypeDetector() {
SystemTypeDetector std = mock(SystemTypeDetector.class);
when(std.getSystemType()).thenReturn(TYPE_C);
return std;
}
}
@Autowired
private SystemTypeDetector systemTypeDetector;
@Test
void contextLoads() {
assertThat(systemTypeDetector.getSystemType()).isEqualTo(TYPE_C);
}
}
Since @TestConfiguration class is a static inner class it will be picked automatically only by this test. Complete mock behaviour that you would put into @Before has to be moved to method that initialises a bean.