'Sets a random value to each of the :fields in :data and makes
sure POST request failed'

def _test_model(self, name, data, fields=None):

    if (fields is None):
        fields = []
    path = (get_path() if (name == 'event') else get_path(1, (name + 's')))
    self._login_user()
    for field in fields:
        data_copy = data.copy()
        data_copy[field] = 'r@nd0m_g00d_for_n0thing_v@lue'
        response = self.post_request(path, data_copy)
        self.assertEqual(response.status_code, 400)
