Use Mockito’s thenCallRealMethod() to Call a Real Method

With Mockito we can Mock an object, stub some of it’s methods but not the other and still be able to call a real method of this stubbed object. In the code example below I am going to share with you how to call a real method of a mocked object using Mockito’s thenCallRealMethod().

In my previous blog post I have shared with you how to Test RESTful Web Service with jUnit and Mockito. The example below will be much simpler and shorter. But if you would like to learn how to add support for JUnit and Mockito to your RESTful Web Service check our this blog post.

The Object to Be Mocked

Below is an example of 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, stub two of it’s method’s 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

We have Mocked the UserProfileEntity and now we can stub two of its method but call a real method on the other one.

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

Use Mockito thenCallRealMethod()

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

Test Class Complete Example

/*
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 * 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.

To learn more about how to use JUnit and Mockito frameworks to test your Restful Web Services check out these video courses and books below:

Testing Your Code with JUnit

JUnit and Mockito Crash Course

Learn how to use JUnit and Mockito and Unit Test in easy steps.

Mockito Tutorial : Learn mocking with 25 Junit Examples

Learn unit testing and mocking with 25 Junit Examples

Happy learning!