'Utility function -- assert there is one success and the state is
plausible'

def assertSuccessful(self, test, result):

    self.assertEqual(result.successes, 1)
    self.assertEqual(result.failures, [])
    self.assertEqual(result.errors, [])
    self.assertEqual(result.expectedFailures, [])
    self.assertEqual(result.unexpectedSuccesses, [])
    self.assertEqual(result.skips, [])
