Mockito – Call a Real Method

Mockito allows us to partially mock an object. This means that we can create a mock object and still be able to call a real method on it.

To call a real method on a mocked object we use Mockito’s thenCallRealMethod().

Also, I have recorded many step-by-step video lessons that teach how to test Java applications. If you are interested to learn more, have a look at my video course “Testing Java with Junit and Mockito“.

The Object to Be Mocked

Below is an example of a Plain Old Java Object which is being used to persist user details into a database. A bit later, when working on a test case, we will mock this object and stub two of its methods which are the getFirstName() and the getLastName() and the getFullName() will be called as a real method rather than stubbed.

package com.appsdeveloperblog.ws.io.entity;

import java.io.Serializable;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;

/**
 *
 * @author skargopolov
 */
@Entity(name = "Profile")
public class UserProfileEntity implements Serializable {

    private static final long serialVersionUID = 7290798953394355234L;

    @Id
    @GeneratedValue
    private long id;
    private String firstName;
    private String lastName;
    private String fullName;

    /**
     * @return the firstName
     */
    public String getFirstName() {
        return firstName;
    }

    /**
     * @param firstName the firstName to set
     */
    public void setFirstName(String firstName) {
        this.firstName = firstName;
    }

    /**
     * @return the lastName
     */
    public String getLastName() {
        return lastName;
    }

    /**
     * @param lastName the lastName to set
     */
    public void setLastName(String lastName) {
        this.lastName = lastName;
    }

    /**
     * @return the id
     */
    public long getId() {
        return id;
    }

    /**
     * @param id the id to set
     */
    public void setId(long id) {
        this.id = id;
    }

    /**
     * @return the fullName
     */
    public String getFullName() {
        if (fullName == null) {
            fullName = getFirstName() + " " + getLastName();
        }

        return fullName;
    }

    /**
     * @param fullName the fullName to set
     */
    public void setFullName(String fullName) {
        this.fullName = fullName;
    }
}

 Use Mockito to Mock an Object 

To Mock UserProfileEntity object, we will annotate it with @Mock annotation and will call the MockitoAnnotations.initMocks(this); in the setUp() method like so:

@Mock
UserProfileEntity userProfileEntity;

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

Stubbing Mock Object with Mockito

Now that you have learned how to mock UserProfileEntity, let’s continue and learn how to stub it with a predefined value.

// Stubbinb userProfileEntity methods
when( userProfileEntity.getFirstName() ).thenReturn( "Sergey" );
when( userProfileEntity.getLastName()).thenReturn( "Kargopolov" );
when( userProfileEntity.getId() ).thenReturn( new Long(1) );

Call a Real Method

To call a real method of a mock object in Mockito we use the thenCallRealMethod() method.

// Call a real method of a Mocked object
when( userProfileEntity.getFullName() ).thenCallRealMethod();

Test Class Complete Example

/*
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 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */
package com.appsdeveloperblog.ws.service.impl;

import com.appsdeveloperblog.ws.TestConfiguration;
import com.appsdeveloperblog.ws.io.dao.Database;
import com.appsdeveloperblog.ws.io.entity.UserProfileEntity;
import com.appsdeveloperblog.ws.service.UsersService;
import com.appsdeveloperblog.ws.shared.dto.UserProfileDto;
import org.junit.*;
import org.junit.runner.RunWith;
import static org.mockito.ArgumentMatchers.any;
import org.mockito.InjectMocks;
import org.mockito.Mock;
import static org.mockito.Mockito.doNothing;
import static org.mockito.Mockito.when;
import org.mockito.MockitoAnnotations;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
 
@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration( classes = TestConfiguration.class )
public class UsersServiceImplTest {

    @Mock
    Database database;

    @Mock
    UserProfileEntity userProfileEntity;
 
    @Autowired
    @InjectMocks
    @Qualifier("usersService")
    UsersService usersService;

    @Before
    public void setUp() {
        MockitoAnnotations.initMocks(this);
    }
    
    @Test
    public void testSaveUserWithFullName()
    {
        //Stubbing Database open and close methods
        doNothing().when(database).openConnection();
        doNothing().when(database).closeConnection();

        // Stubbing userProfileEntity methods
        when( userProfileEntity.getFirstName() ).thenReturn( "Sergey" );
        when( userProfileEntity.getLastName()).thenReturn( "Kargopolov" );
        when( userProfileEntity.getId() ).thenReturn( new Long(1) );
        when( userProfileEntity.getFullName() ).thenCallRealMethod();
        
        // Stubbing database saveUserProfile method
        when( database.saveUserProfile( any(UserProfileEntity.class) ) ).thenReturn( userProfileEntity );

        // Create sample UserProfileDto
        UserProfileDto userProfileDto = new UserProfileDto();
        userProfileDto.setFirstName( "Sergey" );
        userProfileDto.setLastName( "Kargopolov" );
        userProfileDto.setFullName( "Sergey Kargopolov" );

        // Call saveUser method
        UserProfileDto result = usersService.saveUser( userProfileDto );
     
        // Assert expected results
        Assert.assertNotNull( result );
        Assert.assertEquals( userProfileDto.getFirstName() , result.getFirstName() );
        Assert.assertEquals( userProfileDto.getLastName() , result.getLastName() );
        
        Assert.assertNotNull( result.getFullName() );
        Assert.assertEquals( userProfileEntity.getFullName() , result.getFullName() );
    }
}

I hope this little code example was helpful to you. If you are interested in learning more, have a look at other JUnit and Mockito tutorials on this site.

Happy learning!

Video Course: Testing Java with JUnit 5 & Mockito