Question

Possible Duplicate:
Intercept object on method invocation with Mockito

I have an class that can mapp from one format to another. Since this is legacy code I don’t dare to rewrite it, it is basically a set of plugins so if I change one I might have to change all the other. It wasn’t developed with testing in mind.
So this is my problem.

interface Mapper {
    void handle(ClassA classA);
    void handle(ClassB classB);
}

public interface Publisher {
    public void publish(MappedClass mappedClass);
}

class MyMapper implements Mapper {

    private Publisher publisher;
    public void setPublisher(final Publisher publisher) {
        this.publisher = publisher;
    }

    public handle(ClassA classA) {
        final MappedClass mappedClass = // Map from ClassA to MappedClass
        publisher.publish(mappedClass);
    }

    public handle(ClassB classB) {
        final MappedClass mappedClass = // Map from ClassB to MappedClass
        publisher.publish(mappedClass);
    }
}

Okay. So depending on which class was “handled” MappedClass will be published with different values, and it is the values I want to verify (test). The problem is that I will get a test where I first have to write code that tests that the publish method is called,

private boolean wasCalled;

@Test
public void testClassAMapped() {
    wasCalled = false;
    final MyMapper myMapper = new MyMapper();
    myMapper.setPublisher(new Publisher() {
        public void publish(final MappedClass mappedClass) {
            wasCalled = true;
           // Code for verifying the fields in mappedClass
        });
    }
    final ClassA classA = // Create classA
    myMapper.handle(classA);
    assertTrue(wasCalled);
}

So first we create our mock Publisher which will first set the state of wasCalled to true so we know this method was ever called (this example is simplified so there is actually a dispatcher in the code… legacy code so I don’t want to change it), second I want to verify that MappedClass has the correct field values.
What I would like to know is if anyone knows a better way to test this? The wasCalled, and wasCalled check becomes more or less boilerplate code for many of my tests, but since I don’t want to add that much clutter (own hacks, test base classes, etc) I would like to know if there is a way to do this in Mockito, or EasyMock?

Answer 1

Use an Mockito ArgumentCaptor

@Test
public void test(){
  Publisher publisher = Mockito.mock(Publisher.class);
  myMapper.setPublisher(publisher);
  ArgumentCaptor<MappedClass> captor = ArgumentCaptor.forClass(MappedClass.class);

  ....
  myMapper.handle(...);
  ...

  verify(publisher).publish(captor.capture());
  MappedClass passedValue = captor.getValue();
  // assert stuff here
}