def test_iadd(self, evt):
        rval = event.ReturnValue(append_events=[evt])
        rval2 = event.ReturnValue(eat=True, append_events=[evt])
        rset = event.ResultSet()

        rset += rval
        rset += rval2
        rset += None
        assert rset.eat
        assert rset.append_events == [evt, evt]
def test_vice_versa(self):
        class First(Structure):
            pass
        class Second(Structure):
            pass

        First._fields_ = [("second", Second)]

        try:
            Second._fields_ = [("first", First)]
        except AttributeError as details:
            self.assertTrue("_fields_ is final" in
                            str(details))
        else:
            self.fail("AttributeError not raised")