def METHOD_NAME(self):
    self.validator.authenticate_client.side_effect = self.basicauth_authenticate_client
    _, body, _ = self.legacy.create_token_response(
        self.token_uri,
        body='grant_type=password&username=abc&password=secret',
        headers=self.basicauth_client_creds
    )
    self.assertIn('access_token', json.loads(body))