gistfile1.java

@Component
@Accessors(chain=true)
public class ResetPasswordTokenServiceImpl implements ResetPasswordTokenService {
	@Inject @Setter private RandomStringService randomStringService;
	@Inject @Setter private TimeService timeService;
	@Inject @Setter private PasswordResetTokenDao passwordResetTokenDao;
	
	@Override
	public PasswordResetToken generatePasswordResetTokenForUser(UUID userId){
		// instead of using System.currentTimeMillis(), we externalize the call to a service, so we can track it easily
		Long creationTime = timeService.getCurrentTime();
		PasswordResetToken token = new PasswordResetToken();
		token.setUserId(userId)
			.setPasswordResetToken(randomStringService.generateRandomString())
			.setIssuedTimestamp(creationTime)
			.setValidTo(creationTime + DateTimeConstants.MILLIS_PER_DAY);
		passwordResetTokenDao.save(token);
		return token;
	}
}

public class ResetPasswordTokenTest {
	
	private ResetPasswordTokenService resetPasswordTokenService;
	
	private RandomStringService randomStringService;
	private TimeService timeService;
	private PasswordResetTokenDao passwordResetTokenDao;
	
	@Before
	public void setup(){
		// use mocks like me or create your own mocked implementations
		randomStringService = mock(RandomStringService.class); 
		timeService = mock(TimeService.class);
		passwordResetTokenDao = mock(PasswordResetTokenDao.class);
		
		resetPasswordTokenService = new ResetPasswordTokenServiceImpl()
			.setRandomStringService(randomStringService)
			.setTimeService(timeService)
			.setPasswordResetTokenDao(passwordResetTokenDao);
	}
	
	@Test
	public void testResetPasswordTokenHasCorrectIssuedTimestampAndValidTo(){
		UUID userId = UUID.randomId();

		Long currentTime = System.currentTimeMillis();
		String randomString = "someRandomString";
		
		// make the mocked service to always return the currentTime argument
		when(timeService.getCurrentTime()).thenReturn(currentTime);
		when(randomStringService.generateRandomString()).thenReturn(randomString);
		
		ResetPasswordToken token = resetPasswordTokenService.generatePasswordResetTokenForUser(userId);
		
		//mockito will use equality for matching, so you can easily create an instance of what you expect your mock to be called with it and later
		//use it in a matcher
		PasswordResetToken expectedToken = new PasswordResetToken()
			.setUserId(userId)
			.setPasswordResetToken(randomString)
			.setIssuedTimestamp(creationTime)
			.setValidTo(creationTime + DateTimeConstants.MILLIS_PER_DAY);
		
		// verify that the passwordResetTokenDao has been called once with the expected value
		verify(passwordResetTokenDao, times(1)).save(eq(expectedToken));
		
		// now we can easily make assertions about the issued time and the valid to
		assertEquals(currentTime, token.getIssuedOn);
		assertEquals(currentTime + DateTimeConstants.MILLIS_PER_DAY, token validTo);
	}
}