null pointer exception while using mockito

Question

I am totally new to Mockito and have already spent couple of days to write my web app in spring boot. The application runs perfectly fine but I want to learn mockito and want to test some of my class including controller, however I find this testing part so frustrating that I am almost on the verge of skipping this testing part. So I will explain the problem

Controller.java

       @GetMapping("/checkWeather")
        public String checkWeather(@RequestParam(name="city", required=true, defaultValue="Oops! you typed wrong url!")
                                               String city, Map<String,Object> map, Model model)
                throws IOException,HttpClientErrorException.NotFound {
            try{
                Weather result = getWeatherService.getNewWeatherObject(city);
            map.put("weatherList",crudService.getAllWeatherList());
            }catch (HttpClientErrorException e){
                LOGGER.info("Typed City cannot be found, please type name correctly! Aborting program..");
                return "notfound";
            }
            return "weather-history";
        }

I want to test this controller which depends on one service which is:

GetWeatherService.java

@Service
public class GetWeatherService {

    @Autowired
    private ReadJsonObjectService readJsonObjectService;

    public Weather getNewWeatherObject(String city) throws IOException {
        String appid = "47c473417a4db382820a8d058f2db194";
        String weatherUrl = "http://api.openweathermap.org/data/2.5/weather?q="+city+"&APPID="+appid+"&units=metric";
        RestTemplate restTemplate = new RestTemplate();
        String restTemplateQuery = restTemplate.getForObject(weatherUrl,String.class);
        Weather weather = readJsonObjectService.setWeatherModel(restTemplateQuery);
        return weather;
    }
}

Now to test my controller i have written this test:

WeatherRestControllerTest.java

@AutoConfigureMockMvc
@RunWith(SpringJUnit4ClassRunner.class)
@SpringBootTest
public class WeatherRestControllerTest extends AbstractTestNGSpringContextTests {

private Weather weather;

@Autowired
private MockMvc mockMVC;

@InjectMocks
private WeatherRestController weatherRestController;

@Before
public void setUp() {
    MockitoAnnotations.initMocks(this);

}

@Test
public void testCheckWeather() throws Exception {
    GetWeatherService getWeatherService = Mockito.mock(GetWeatherService.class);
    Mockito.when(getWeatherService.getNewWeatherObject("Munich")).thenReturn(new Weather());
    mockMVC.perform(MockMvcRequestBuilders.get("/checkWeather?city=Munich")).
    andExpect(MockMvcResultMatchers.status().isOk()).
    andExpect(MockMvcResultMatchers.content().string("weather-history"));
    }
}

But in the end on running the test I get this exception:

java.lang.NullPointerException
    at com.weatherapi.test.weather_api.rest.WeatherRestControllerTest.getWeatherRest(WeatherRestControllerTest.java:42)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
    at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
    at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
    at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
    at org.springframework.test.context.junit4.statements.RunBeforeTestExecutionCallbacks.evaluate(RunBeforeTestExecutionCallbacks.java:74)
    at org.springframework.test.context.junit4.statements.RunAfterTestExecutionCallbacks.evaluate(RunAfterTestExecutionCallbacks.java:84)

I get NullPointerException and I have no idea what is going wrong. Why its throwing null. I am trying from morning to understand syntax but I am getting nothing. I spent couple of time researching and changing syntax but getting same error. Why it is so complicated and I still don't understand what is the purpose of doing all this.

EDIT:

I now have new implementation for WeatherRestcontrollerTest.java above. This I did as per the inputs in comments.

Answer 1

Ensure that the mockMvc gets injected properly.

Add @AutoConfigureMockMvc to your test so that your test class declaration looks like:

@AutoConfigureMockMvc
@RunWith(SpringJUnit4ClassRunner.class)
@SpringBootTest
public class WeatherRestControllerTest extends AbstractTestNGSpringContextTests

Also ensure that the mockMvc is @Autowired

@Autowired
private MockMvc mockMVC;

This way the mockMvc gets injected.