'Test that the supportsInterface method behaves appropriately.'

def test_supportsInterface(self):

    options = OptionsForUsernamePassword()
    self.assertTrue(options.supportsInterface(credentials.IUsernamePassword))
    self.assertFalse(options.supportsInterface(credentials.IAnonymous))
    self.assertRaises(strcred.UnsupportedInterfaces, options.addChecker, self.anonChecker)
