}
	bodyBytes, _ := io.ReadAll(res.Body)
	if g, e := string(bodyBytes), backendResponse; g != e {
		t.Errorf("got body %q; expected %q", g, e)
	}
}

type RoundTripperFunc func(*http.Request) (*http.Response, error)

func (fn RoundTripperFunc) RoundTrip(req *http.Request) (*http.Response, error) {
	return fn(req)
}

// Issue 16036: send a Request with a nil Body when possible

			}

			// Error
			if responder.called {
				t.Errorf("Unexpected proxy handler error: %v", responder.err)
			}
		}()
	}
}

type RoundTripperFunc func(req *http.Request) (*http.Response, error)

func (fn RoundTripperFunc) RoundTrip(req *http.Request) (*http.Response, error) {
	return fn(req)
}

func TestProxyUpgrade(t *testing.T) {

	localhostPool := x509.NewCertPool()