Printing statements in thenReturn of mockito

Question

I am using Mockito to mock a certain class while writing my test cases.

Is there a way to print some statements before returning a value? Like:

when(x.callFunction(10).thenReturn(new String("Hello"));

The above statement works, however I am not able to do the following:

when(x.callFunction(10).thenReturn({
   System.out.println("Mock called---going to return hello");
   return new String("Hello");});

Answer 1

With thenAnswer you can execute additional actions every time the mocked method is invoked.

when(x.callFunction(10)).thenAnswer(new Answer<String>() {
    public String answer(InvocationOnMock invocation)  {
        System.out.println("Mock called---going to return hello");
        return "Hello";
    }
});

See also thenAnswer Vs thenReturn.

Answer 2

If the object you're going to create is not final, then besides thenAnswer provided by @Roland Weisleder, you can just use an anonymous subclass with init block in thenReturn, like the following example code:

class FoobarFactory {
    public Foobar buildFoobar() {
        return null;
    }
}

class Foobar {
    private String name;
    public Foobar(String name) {
        this.name = name;
    }

    public String getName() {
        return name;
    }
}

with mock code as:

@Test
public void testFoobar() throws Exception {
    FoobarFactory foobarFactory = mock(FoobarFactory.class);
    when(foobarFactory.buildFoobar()).thenReturn(new Foobar("somename") {
        {
            System.out.println("Creating mocked Foobar");
        }
    });

    Foobar foobar = foobarFactory.buildFoobar();
    assertThat(foobar.getName(), is("somename"));
}