IMethods mock = mock(IMethods.class);
//some stubbing
when(mock.simpleMethod(1)).thenReturn("foo");
when(mock.otherMethod()).thenReturn("foo");
when(mock.booleanObjectReturningMethod()).thenReturn(false);
//stub called with different args:
String ret = mock.simpleMethod(2);
//assertion fails due to stub called with different args