mock instance is null after @Mock annotation

Question

I try to run this test:

    @Mock IRoutingObjHttpClient routingClientMock;
    @Mock IRoutingResponseRepository routingResponseRepositoryMock;


    @Test
    public void testSendRoutingRequest() throws Exception {
        CompleteRoutingResponse completeRoutingResponse = new CompleteRoutingResponse();
        completeRoutingResponse.regression_latencyMillis = 500L;

        Mockito.when(routingClientMock.sendRoutingRequest(any(RoutingRequest.class))).thenReturn(completeRoutingResponse);

        RoutingObjHttpClientWithReRun routingObjHttpClientWithReRun = new RoutingObjHttpClientWithReRun
                (routingClientMock, routingResponseRepositoryMock);

...
    }

but I get NullPointerException for:

Mockito.when(routingClientMock.

what am i missing?

Answer 1

When you want to use the @Mock annotation you should use the MockitoJUnitRunner

@RunWith(MockitoJUnitRunner.class)
public class MockitoTest {

    @Mock
    private IRoutingObjHttpClient routingClientMock;

    @Test
    public void testSendRoutingRequest() throws Exception {
        // ...
    }

}

See also this tutorial.

Answer 2

Same problem can occur if you are using Junit5 since there is no more '@RunWith' annotation.

In this case you should annotate your class with:

@ExtendWith(MockitoExtension.class)
public class MyTestClass {
...

You should also import into your dependency (Maven - pom.xml):

<dependency>
    <groupId>org.mockito</groupId>
    <artifactId>mockito-junit-jupiter</artifactId>
    <version>${mockito.version}</version>
    <scope>test</scope>
</dependency>

Answer 3

You have three options for activating the @Mock annotation: MockitoRule, MockitoJUnitRunner, MockitoAnnotations.initMocks(this). IMHO using the MockitoRule is the best one, because it lets you still choose another runner like e.g. Parameterized.

Use the MockitoRule

public class MockitoTest {

  @Mock
  private IRoutingObjHttpClient routingClientMock;

  @Rule
  public MockitoRule rule = MockitoJUnit.rule();

  @Test
  public void testSendRoutingRequest() throws Exception {
    // ...
  }
}

Use the MockitoJUnitRunner

@RunWith(MockitoJUnitRunner.class)
public class MockitoTest {

  @Mock
  private IRoutingObjHttpClient routingClientMock;

  @Test
  public void testSendRoutingRequest() throws Exception {
    // ...
  }
}

Call MockitoAnnotations.initMocks(this) explicitly.

This can be done in qn @Before method, in your own runner or in an own rule.

public class MockitoTest {

  @Mock
  private IRoutingObjHttpClient routingClientMock;

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

  @Test
  public void testSendRoutingRequest() throws Exception {
    // ...
  }
}

Answer 4

If you use junit.jupiter with @ExtendWith(MockitoExtension.class) for test class but mocks are null, ensure that @Test annotation is imported from

import org.junit.jupiter.api.Test;

instead of org.junit.Test;

Answer 5

What solved this issue for me (combination of answers above and my own additions):

• MockitoAnnotations.initMocks(this); in the @Before method
• Test class must be public
• Test methods must be public
• import org.junit.Test; instead of import org.junit.jupiter.api.Test;

When doing command + N --> Test... in Intellij it generates (as a default at least) some boilerplate that did not work in my case.

Answer 6

For me, even after adding @RunWith(MockitoJUnitRunner.class) it was not working.
Turned out, I had made the silly mistake of importing @Test from

import org.junit.jupiter.api.Test;

instead of

import org.junit.Test;

After correcting it, it worked!

Answer 7

Add @ExtendWith(MockitoExtension.class) annotation to the test class and it should work given You are using Junit 5+ version. If you are using older version of Junit use @RunWith(MockitoJUnitRunner.class) annotation.

Answer 8

1. You should use @RunWith(SpringJUnit4ClassRunner.class) at your class
2. You have to call MockitoAnnotations.initMocks(this); in @Before method

Answer 9

It can also be an import problem, so make sure you have the appropriate imported package.

For example, the "org.easymock" package also does have an annotation called @Mock, which of course, won't work with Mockito specific setup.

Answer 10

I had the problem that I declared @Mock MyClass myClass and then tried to mock a behaviour inside my @BeforeAll annotated method:

@Mock
private MyClass myClass;

...

@BeforeAll
public void init()
{
    ...
    Mockito.when(myClass.something()).thenReturn("Not found")
    ...
}

Apparently init() was executed before the mock initialization of myClass, so myClass == null inside init().

The solution was to change the annotation from @BeforeAll to @BeforeEach.

Answer 11

For me it worked when I added :

1. At class level:

@RunWith(MockitoJUnitRunner.class).

2. Inside class:

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

Answer 12

Try to to check if the method that you are calling is a final method or not.

Mockito cannot mock the final method. https://github.com/mockito/mockito/wiki/FAQ

Answer 13

Junit 5 with InjectMocks. Based on above suggestion https://stackoverflow.com/a/55616702/2643815

 @ExtendWith(MockitoExtension.class)
public class MyClientTest {
@Mock
    Environment environment;
    @Mock
    ClassCreator classCreator;

    @InjectMocks
    MyClient myClient;


    @Test
    public void mytest() {
            myClient = new MyClient(environment, classCreator);
            
            }
            }

Answer 14

For me adding the annotation to the class:

@RunWith(MockitoJUnitRunner.class)

and modifying the version of Mockito solved this issue.

<dependency>
        <groupId>org.mockito</groupId>
        <artifactId>mockito-core</artifactId>
        <version>2.23.4</version>
        <scope>test</scope>
</dependency>

Answer 15

I had the same issue, but I found updating my tests (which were originally written for JUnit 3 and used the legacy setUp() and tearDown() methods) to JUnit 4 and modern annotated fixture methods worked.

Additionally, if you're using the Rule:

@Rule public MockitoRule rule = MockitoJUnit.rule();

Make sure the rule is also on a public class or you will receive the message:

How did getFields return a field we couldn't access?

Answer 16

Found this solution in comments that worked for me. Do this for all the mocks you are creating.

You need to instantiate the routingClientMock e.g.

routingClientMock = Mockito.mock(RoutingObjHtttpClient.class);

Answer 17

My issue was that I was trying to mock an object which was final in my service. Just needed to remove final and it worked.

Answer 18

our application uses JUNIT5 , same issue occured. I replaced @Mock with @InjectMocks - then issue was resolved

Answer 19

If you are also using PowerMock then

@RunWith(MockitoJUnitRunner.class)

can be replaced with

@RunWith(PowerMockRunner.class)

This will activate your @Mocks and enable the PowerMock functionality.