public HttpContent CreateContentWithHeaders(HttpContentHeaders contentHeaders) { var headers = contentHeaders.ToNameValueCollection(); var newContent = CreateContent(); foreach (string?header in headers) { var values = headers.GetValues(header); // This method will never return false, cause we get headers from HttpContentHeaders // I can't create any unit tests that will cause return false newContent.Headers.TryAddWithoutValidation(header, values); } return(newContent); }