def METHOD_NAME(self):
    x = yield process_chain([cb1, cb2, cb3], "res", "v1", "v2")
    self.assertEqual(x, "(cb3 (cb2 (cb1 res v1 v2) v1 v2) v1 v2)")
    gotexc = False
    try:
        yield process_chain([cb1, cb_fail, cb3], "res", "v1", "v2")
    except TypeError:
        gotexc = True
    self.assertTrue(gotexc)