[FIXED] Java Dependency Injection Unit Testing

Issue

Can somebody make an junit test on this class?

public class MyApplication {
    private EmailService email = new EmailService();

    public boolean processMessages (String msg , String recipient ) {
        if (msg.length ==0 | | recipient.length ==0 ) {
            return false ;
        }
        return this.email.sendEmail (msg , recipient ) ;
    }
}

Solution

Your title makes the problem clear: you are not injecting the dependency on EmailService. To do that, add a setter or (better) make it final and add it to the constructor.

That'd look like:

public class MyApplication {
    private final EmailService email;

    public MyApplication(EmailService email) {
        this.email = email;
    }

    public boolean processMessages (String msg , String recipient ) {
        if (msg.length == 0 || recipient.length == 0 ) {
            return false ;
        }
        return this.email.sendEmail (msg , recipient ) ;
    }
}

And an appropriate test might be (using junit and mockito):

private MyApplication app;
private EmailService email;

@BeforeEach
void setup() {
    email = mock(EmailService.class);
    when(email.sendEmail(any(), any())).thenReturn(true);
    app = new MyApplication(email);
}

@Test
void testProcessZeroLengthMessageOrPerson() {
    assertFalse(app.processMessages("", "Person"));
    assertFalse(app.processMessages("Message", "")):
    assertFalse(app.processMessages("", "")):
}

@Test
void testProcessMessage() {
    assertTrue(app.processMessage("Message", "Person"));
    verify(email).sendEmail("Message", "Person");
}

Answered By - sprinter