return func(rec *ResponseRecorder) error {
			if got := rec.Result().Header.Get(key); got != want {
				return fmt.Errorf("final header %s = %q; want %q", key, got, want)
			}
			return nil
		}
	}
	hasNotHeaders := func(keys ...string) checkFunc {
		return func(rec *ResponseRecorder) error {
			for _, k := range keys {
				v, ok := rec.Result().Header[http.CanonicalHeaderKey(k)]
				if ok {