'If default_impersonation=TEST_USER, tests that the job defaults
to running as TEST_USER for a test without run_as_user set'

def test_default_impersonation(self):

    os.environ['AIRFLOW__CORE__DEFAULT_IMPERSONATION'] = TEST_USER
    try:
        self.run_backfill('test_default_impersonation', 'test_deelevated_user')
    finally:
        del os.environ['AIRFLOW__CORE__DEFAULT_IMPERSONATION']
