Junit & Mock Framework Mockito Code Samples – Part 1

Software Requirement

The goal is to create a simple piece of software which caters to the requirement of school admission where in applicants submit their admission application.

Class Design & JUnit Tests

To meet above requirement, following different component is designed:

• Core Components (Key Ones)
  • AdmissionApplication.java: Consists of method recordNewApplication which validates the submitted application, and later, stores in the database after successful validation.
  • ApplicationValidation.java: Consists of methods for validating business rules associated with admission such as mandatory inputs (first name, last name, class, gender, date of birth etc)
  • AdmissionApplicationDAO.java: Stores the data into database
• Junit Tests
  • AdmissionApplicationTest: Junit tests for testing AdmissionApplication methods
  • ApplicationValidationTest: Junit tests for testing ApplicationValidation methods

Source Code: AdmissionApplication.java

public class AdmissionApplication {

	private AdmissionApplicationDAO admissionApplicationDao;
	private ApplicationValidation applicationValidation;

	public AdmissionApplication() {		
	}

	public ApplicationResult recordNewApplication( Applicant applicant ) {
		ApplicationResult result = null;

		result = applicationValidation.validate( applicant ); 
		if( !result.isSuccess() ) {
			return result;
		} 

		result = admissionApplicationDao.persist(applicant);

		if( result.isSuccess() ) {
			result.setMessage( "Admission application successful" );
		} else {
			result.setMessage( "Admission application failed" );
		}

		return result;
	}

	public AdmissionApplicationDAO getAdmissionApplicationDao() {
		return admissionApplicationDao;
	}

	public void setAdmissionApplicationDao(
			AdmissionApplicationDAO admissionApplicationDao) {
		this.admissionApplicationDao = admissionApplicationDao;
	}

	public ApplicationValidation getApplicationValidation() {
		return applicationValidation;
	}

	public void setApplicationValidation(ApplicationValidation applicationValidation) {
		this.applicationValidation = applicationValidation;
	}
}

Source Code (Junit with Mocking): AdmissionApplicationTest.java

In the source code below, following points should be noted:

1. @Mock annotation is used to represent classes/components whose mocks will be used
2. Once you annotated mock components, MockitoAnnotations.initMocks(this) is used to initialize these mocks. The code could be seen inside setUp() method.
3. Mockito.when(…).thenReturn(…): It is used for stubbing. Once stubbed, the method will always return stubbed value regardless of how many times it is called.
4. Mockito.verify(…).methodName(..): It is used to verify the method invocation.

The important point to note is that mocks have been created for two objects such as ApplicationValidation, and AdmissionApplicationDAO. That implies that code of AdmissionApplication is tested in isolation by mocking dependent classes.

public class AdmissionApplicationTest {

	private AdmissionApplication aa;
	@Mock
	private ApplicationValidation appValidation;
	@Mock
	private AdmissionApplicationDAO aaDao;

	@Before
	public void setUp() throws Exception {
		MockitoAnnotations.initMocks(this);
		aa = new AdmissionApplication();			
		aa.setApplicationValidation( appValidation );
		aa.setAdmissionApplicationDao( aaDao );

	}

	@After
	public void tearDown() throws Exception {
		aa = null;
		appValidation = null;
		aaDao = null;
	}

	@Test
	public void applicationSuccessfulIfAllDetailsGiven() {
		Applicant applicant = new Applicant();				
		ApplicationResult result = new ApplicationResult();
		result.setSuccess( true );

		Mockito.when( appValidation.validate(applicant) ).thenReturn( result );
		Mockito.when( aaDao.persist(applicant)).thenReturn( result );

		result = aa.recordNewApplication( applicant );
		assertTrue( result.isSuccess() );
	}

	@Test
	public void applicationFailureIfValidationFailed() {
		Applicant applicant = new Applicant();				
		ApplicationResult result = new ApplicationResult();
		result.setSuccess( false );
		Mockito.when( appValidation.validate(applicant) ).thenReturn( result );

		result = aa.recordNewApplication( applicant );

		Mockito.verify(appValidation).validate(applicant);
		Mockito.verify(aaDao, Mockito.never()).persist(applicant);
		assertFalse( result.isSuccess() );
	}

	@Test
	public void applicationFailureIfDBPersistenceFailed() {
		Applicant applicant = new Applicant();				
		ApplicationResult result = new ApplicationResult();

		result.setSuccess( true );
		Mockito.when( appValidation.validate(applicant) ).thenReturn( result );
		result.setSuccess( false );
		Mockito.when( aaDao.persist(applicant) ).thenReturn( result );

		result = aa.recordNewApplication( applicant );
		assertFalse( result.isSuccess() );
	}

}