func (w *tunnelingResponseWriter) Write(p []byte) (int, error) {
	w.mu.Lock()
	defer w.mu.Unlock()
	if w.hijacked {
		klog.Errorf("Write called after hijack")
		return 0, http.ErrHijacked
	}
	w.written = true
	return w.w.Write(p)
}

// WriteHeader is delegated to the stored "http.ResponseWriter".
func (w *tunnelingResponseWriter) WriteHeader(statusCode int) {
	w.mu.Lock()

	trw.hijacked = true
	_, err = trw.Write(expectedWrite)
	assert.Error(t, err, "Writing to ResponseWriter after Hijack() is an error")
	assert.True(t, errors.Is(err, http.ErrHijacked), "Hijacked error returned if writing after hijacked")
	// Validate WriteHeader().
	trw = &tunnelingResponseWriter{w: &mockResponseWriter{}}
	expectedStatusCode := 201