Cannot invoke "PacienteService.findById(java.lang.Integer)" because "this.service" is null

Question

I'm trying test a RestAPI in Java, but I can't mock my Service class

When start test, it gives me an error: java.lang.NullPointerException: Cannot invoke "com.tcc.tccbackend.services.PacienteService.findById(java.lang.Integer)" because "this.service" is null .

Code:

@WebMvcTest(PacienteController.class)
public class PacienteTest extends BaseTest {

@Mock
    private PacienteService service;

@Autowired
    private MockMvc mockMvc;

@BeforeEach
    public void setup() {
        RestAssuredMockMvc.mockMvc(mockMvc);
    }

@Test
    @DisplayName("Retorna sucesso quando busca um paciente ")
    public void t4() {
        Mockito.when(service.findById(9999))
                .thenReturn(new Paciente(9999, "Gilberson", "gilber@gmail.com", "68211836104", "(67) 99625-5371", new Date(), List.of()));
        RestAssuredMockMvc
                .given()
                .header("Authorization", getJWT())
                .accept(ContentType.JSON)
                .when()
                .get("/pacientes/9999")
                .then().statusCode(200);
    }

BaseTest.class:

public class BaseTest {
    public BaseTest(){
        baseURI = "http://localhost";
        port = 8080;
        basePath = "/api";
    }

    public static String getJWT() {
        return given()
                .body("{\n" + "\t\"email\": \"paula@gmail.com\",\n" + "\t\"senha\": \"senha\"\n" + "}")
                .contentType(ContentType.JSON)
                .when()
                .post("/user/login")
                .then()
                .extract()
                .path("token");
    }
}

Versions:

• Java 17
• RestAssured 5.3.0
• SpringBoot 2.7.0
• SpringBoot Starter Test 2.7.0
• Junit 4.13.2

Answer 1

Your mixing up unit test and integration test config.

Annotations for unit tests look like this:

@ExtendWith(MockitoExtension.class)
class MyTest {

    @Mock
    private ServiceA myMock;

    @Spy
    private ServiceB mySpy;

    @InjectMocks
    private ServiceC myClassUnderTest;

    @Test
    void receive() {
         // test logic
    }

}

Annotations for integration tests look like this:

@ActiveProfiles("test")
@SpringBootTest
class MyTest {

    @MockBean
    private ServiceA myMock;

    @SpyBean
    private ServiceB mySpy;

    @Autowired
    private ServiceC myClassUnderTest;

    @Test
    void receive() {
         // test logic
    }

}

I don't know about your test config because you didn't post it here, but I suppose you should use @MockBean instead of @Mock for PacienteService service .