SetRSTAvoidanceDelay(t, timeout)
		t.Logf("set RST avoidance delay to %v", timeout)

		const bodySize = 5 << 20
		req := []byte(fmt.Sprintf("POST / HTTP/1.1\r\nHost: foo.com\r\nContent-Length: %d\r\n\r\n", bodySize))
		for i := 0; i < bodySize; i++ {
			req = append(req, 'x')
		}

		cst := newClientServerTest(t, mode, HandlerFunc(func(w ResponseWriter, r *Request) {

			io.Copy(io.Discard, conn)
			copying.Done()
		}()
	})).ts
	c := ts.Client()

	const bodySize = 256 << 10
	finalBit := make(byteFromChanReader, 1)
	req, _ := NewRequest("POST", ts.URL, io.MultiReader(io.LimitReader(neverEnding('x'), bodySize-1), finalBit))
	req.ContentLength = bodySize
	res, err := c.Do(req)
	if err := wantBody(res, err, "foo"); err != nil {
		t.Errorf("POST response: %v", err)
	}