Spring Security - Integration Tests with user

Question

I have an integration test for Spring (with Spring Security) that looks like this:

@RunWith(SpringRunner.class)
@SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT)
public class RootControllerIT {
    @LocalServerPort
    private int port;

    private URL base;

    @Autowired
    private TestRestTemplate template;

    @Before
    public void setUp() throws Exception {
        this.base = new URL("http://localhost:" + port + "/");
    }

    @Test
    @WithMockUser
    public void getHello() throws Exception {
        ResponseEntity<String> response = template.getForEntity(base.toString(),
                String.class);
        assertThat(response.getBody(), equalTo("OK"));
    }
}

My issue is that the @WithMockUser does not work here, is there a way to add a mock user to the TestRestTemplte or otherwise send authenticated user information to the Integration test?

The mock user works fine when using MockMvc to test, but it's obviously not appropriate here.