t.Error("body length is zero")
		}
	})).ts
	c := ts.Client()
	c.Transport.(*Transport).RegisterProtocol("http", roundTripFunc(func(r *Request) (*Response, error) {
		// Draining body to trigger failure condition on actual request to server.
		if n, _ := io.Copy(io.Discard, r.Body); n == 0 {
			t.Error("body length is zero during round trip")
		}
		return nil, ErrSkipAltProtocol
	}))

	// and then advances the head pointer because we don't want to mess up the statuses of G's
	// while runqdrain() and runqsteal() are running in parallel.
	// Thus we should advance the head pointer before draining the local P into a gQueue,
	// so that we can update any gp.schedlink only after we take the full ownership of G,
	// meanwhile, other P's can't access to all G's in local P's runnable queue and steal them.