myUrl field is null even though I set it in test setup

I have this test:

@RunWith(MockitoJUnitRunner.class)
public class CollectionManagerTest {

    @InjectMocks
    private CollectionManager collectionManager;

    @Mock
    RestTemplate restTemplate;

    @Captor
    private ResponseEntity<String> responseEntity;

    /**
     *
     */
    @Before
    public void setup() {
        org.springframework.test.util.ReflectionTestUtils.setField(collectionManager, "myUrl", "http://test");
        responseEntity = new ResponseEntity<>("SUCCESS", HttpStatus.OK);
    }

    @Test
    public void createMyStringTest() throws Exception {
        String myString = collectionManager.createMyString("TestDocIsns");
        assertTrue(myString.contains("DOC_ISN=TestDocIsns"));
    }
}

It fails with this error:

ReflectionTestUtils - Setting field 'myUrl' of type [null] on target object [org.me.services.docs.CollectionManager@2dc9b0f5] or target class [class org.me.docs.CollectionManager] to value [http://test]

I thought this would have been set with org.springframework.test.util.ReflectionTestUtils.setField(collectionManager, "myUrl", "http://test");

This is the variable in the actual class:

@Value("${my.url}")
private String myUrl;

What am I doing wrong?