jmockit return the same object

Question

Can I mock a method using JMockit in a way that it returns the argument that was passed to it?

Consider a signature like this;

public String myFunction(String abc);

I see it is possible to do this using Mockito. But is this doable in JMockit?

Answer 1

The JMockit manual provides some guidance... I really suggest you read it. The construct you are looking for would probably look something like this:

@Test
public void delegatingInvocationsToACustomDelegate(@Mocked final DependencyAbc anyAbc)
{
   new Expectations() {{
      anyAbc.myFunction(any);
      result = new Delegate() {
         String aDelegateMethod(String s)
         {
            return s;
         }
      };
   }};

   // assuming doSomething() here invokes myFunction()...
   new UnitUnderTest().doSomething();
}

Answer 2

JMockit can also capture arguments:

@Test
public void testParmValue(@Mocked final Collaborator myMock) {

    // Set the test expectation.
    final String expected = "myExpectedParmValue";

    // Execute the test.
    myMock.myFunction(expected);

    // Evaluate the parameter passed to myFunction.
    new Verifications() {
        { 
            String actual;
            myMock.myFunction(actual = withCapture());

            assertEquals("The parameter passed to myFunction is incorrect", expected, actual);
        }
    };
}