Java testing with mockito: mock class object

Question

I would like to mock an object inside my class.

public class Controller{

   private StandardEmailSender sender = new StandardEmailSender();

    public void process() throws EmailException {
       // do some stuff
       sender.sendEmail(to, subject, body);
       // do some stuff
    }
 }

I would like to mock sender.sendEmail(to, subject, body);. I've spent time finding a solution but I'm stuck. I tried to mock directly the object StandardEmailSender like this :

@Mock
StandardEmailSender sender;

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

    doNothing().when(sender).sendEmail(anyString(), anyString(), anyString());
}

@Test
public void test() throws EmailException {
    Controller controller= new Controller ();
    controller.process();

    //make some asserts
}

Would someone have a solution to my problem? Thanks!

GhostCat · Accepted Answer · 2017-10-18 10:47:55Z

3

You have two choices here:

make it possible for your test case to "manually" inject a (mocked) Sender object (for example by providing a constructor to set that field)
make use of Mockitos @InjectMocks annotation

A typical approach for option 1 is to use constructor telescoping, like this:

public class Controller {

 private final Sender sender;

 public Controller() { this(new StandardEmailSender()); }
 Controller(Sender sender) { this.sender = sender; }

By doing so, clients can still create a Controller instance without worrying about providing a sender, and your unit tests can use that package protected constructor to provide a mocked sender instance.

edited Oct 18, 2017 at 10:47

answered Oct 18, 2017 at 10:44

GhostCat

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1 Comment

GhostCat Over a year ago

@Kagelmacher Yes it does. But some people still dislike it: tedvinke.wordpress.com/2014/02/13/… ... and in case you find my answer sufficient, please dont forget about accepting at some point.

M. le Rutte · Accepted Answer · 2017-10-18 10:45:32Z

1

Use a form of dependency injection, for example:

public class Controller{
   private final EmailSender sender;

   Controller(EmailSender emailSender) {
       this.sender = Objects.requireNonNull(emailSender); 
   }

   public Controller() {
      this(new StandardEmailSender());
   }     
}

In your test:

@Test
public void test() throws EmailException {
    Controller controller= new Controller(mockedSender);
    controller.process();
}

answered Oct 18, 2017 at 10:45

M. le Rutte

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