Mockito Mock Objects Returns Null

Mockito mock objects returns null

It really depends on GeneralConfigService#getInstance() implementation. Also you can simplify your test code a lot if you use @InjectMocks annotation.

When using MockitoJUnitRunner you don't need to initialize mocks and inject your dependencies manually:

@RunWith(MockitoJUnitRunner.class)
public class GeneralConfigServiceImplTest  {

    @InjectMocks
    private GeneralConfigService generalConfigService;

    @Mock
    private GeneralConfigDAO generalConfigDAO;

    @Test
    public void testAddGeneralConfigCallDAOSuccess() {
       // generalConfigService is already instantiated and populated with dependencies here
       ...
    }
}

Mocked object returning null

From the comments you tell that Connector4AuroraDB is autowired by Spring(@Autowired).
It seems to me that you are using field injections, which makes it difficult to do stub dependencies.

I assume you have something like:

public class AuroraRepoImpl {
  @Autowired private Connector4AuroraDB connector4AuroraDB;
}

For this to work you need a Spring context setup, so spring can look into the bean registry to find the dependency.

Your example is a simple unit test running with MockitoJUnitRunner.
You should change your implementation to use injection by constructor, this way Mockito can inject the dependency:

public class AuroraRepoImpl {
  private final Connector4AuroraDB connector;

  @Autowired
  public AuroraRepoImpl(final Connector4AuroraDB connector) {
    this.connector = connector;
  }
}

If you use a new Spring version you can even omit the @Autowired annotation if the class only has one constructor.

Why does Mockito return null when I specify an Optional of my type

I believe it is because you forget to mock the method PunishmentValidator#validatePunishmentName("mute") to return true such that the method that you stub on PunishmentService is never invoked because by default if you do not stub a method , it will return false (see this).

Also it is a known behaviour that @MockBean is configured as lenient stubbing which will not reported error (i.e. throw UnnecessaryStubbingException) if you stub a method but it actually does not get executed.

So change the following should fix your problem :

@Test
public void getPunishmentTypeReturnsMuteWhenMuteIsSpecified() throws Exception {
    Optional<Punishment> mute = Optional.of(new Punishment("mute"));
    
    Mockito.when(punishmentService.getPunishmentType("mute")).thenReturn(mute);
    Mockito.when(punishmentValidator.validatePunishmentName("mute")).thenReturn(true);

    mvc.perform(get("/api/punishments/mute"))
            .andExpect(status().isOk())
            .andExpect(jsonPath("$.punishmentName", Matchers.equalTo("mute")));
}

Mockito Mocked Class returns Null

The way to use Mockito is

private DescribeHiveTable mockObj; // must be accessible to Test methods

@Before
public void initialize(){
    this.mockObj = Mockito.mock(DescribeHiveTable.class);
    <etc>
}

@Test
public void testComplexFeaturesExistingRun() {
    /* test the objects that are set up to use this.mockObj,
       and not the usual type of DescribeHiveTable */
}

Note that

describeTable = new DescribeHiveTable();

means that you're using a new, unmocked, DescribeHiveTable, not the mocked mockObj.

But it looks like you don't have control over the DescribeHiveTable instance used by the DriverClass? If that's the case then either

• Mockito isn't going to help you -- or you at least have to mock the DriverClass too; or
• you have to use reflection to replace the describeTable in DriverClass with mockObj.

Mockito mocked method is returning NULL

A working example of your requirement could be:

@RunWith(MockitoJUnitRunner.class)
public class MemberTest {
    @InjectMocks
    private Member member;
    @Mock
    private MemberDao memberDao;

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

    @Test
    public void createId() throws Exception {
        MembersIdDto dto = new MembersIdDto();
        dto.setId("967405286");
        when(memberDao.findNext()).thenReturn(dto);

        assertThat(member.createNewId()).isEqualTo("967405286");
    }
}

…with the classes-under-test…

public class Member {
    @Resource
    MemberDao memberDao;

    public String createNewId() {
        return memberDao.findNext().getId();
    }
}

…and…

public class MemberDao {
    public MembersIdDto findNext() {
        return null; // or whatever
    }
}

…and…

import lombok.Data;
import lombok.NoArgsConstructor;

@Data
@NoArgsConstructor
public class MembersIdDto {
    private String id;
}

By the way, I use the AssertJ assertion framework and with member.createNewId() you have now a real call on production code.

Mocked method is returning null instead of expected object

When you partially mock static methods of a class, you need to explicitely state if real implementation should be called (check thenCallRealMethod below).

If you don't that, any method you call would be treated as a method on a mock without specified behaviour, and thus return null.

On top of that:

• you use EJBFacades which was not posted in the question. I've rewritten the test in terms of XYZClass
• your assertion will fail, as you return a subclass of the service.

package com.test.powermock.teststacitejb;

import org.junit.Before;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.mockito.Mockito;
import org.powermock.api.mockito.PowerMockito;
import org.powermock.core.classloader.annotations.PrepareForTest;
import org.powermock.modules.junit4.PowerMockRunner;

import javax.naming.InitialContext;

import static org.junit.Assert.assertTrue;

@RunWith(PowerMockRunner.class)
@PrepareForTest(XYZClass.class)
public class XYZClassTest {


    private InitialContext ctx;

    @Before
    public void setUp() throws Exception {
        PowerMockito.mockStatic(XYZClass.class);
        ctx = Mockito.spy(new InitialContext());
        PowerMockito.doReturn(ctx).when(XYZClass.class, "getCtx");

        IMFTPManagerBean service1 = new IMFTPManagerBean();
        Mockito.doReturn(service1).when(ctx).lookup(Mockito.eq("abc"));
        PowerMockito.when(XYZClass.getIMFTPManagerFacade()).thenCallRealMethod();
    }


    @Test
    public void testGetIMFTPManagerFacade() {
        IMFTPManagerService service = XYZClass.getIMFTPManagerFacade();
        assertTrue(service instanceof IMFTPManagerService);
    }
}

Mocked object returns null

It's most likely returning null because your parameter definition in when and the actual parametes differ. In your case it's very likely that your mocked entity and the HttpEntity you're creating in your code under test are neither the same nor equal. So you need to widen your expectations in the when-definition. You should use Matchers in your definition and the could use isA(HttpEntity.class) for your entity.

Mockito when()...then() methods not returning the expected mock object (returns null), what am I doing wrong?

Using @InjectMocks seems to be wrong here.

After removing that annotation and instantiating the class in the test itself I can get things working.

This also meant I no longer needed attributes and internal classes to be static.

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