total_bytes = 0
                start_time = time.perf_counter()
                
                for download_url in urls_to_download:
                    with session.get(download_url, stream=True, timeout=5, verify=False) as r:
                        r.raise_for_status()
                        for chunk in r.iter_content(chunk_size=16384):
                            if self._is_aborted:
                    return None
                    
                            if chunk:
                    total_bytes += len(chunk)
                    
                            elapsed = time.perf_counter() - start_time
                            if elapsed >= test_duration:
                    break
                    
                    elapsed = time.perf_counter() - start_time
                    if elapsed >= test_duration:
                        break

                elapsed = time.perf_counter() - start_time
                if elapsed > 0:
                    (Bytes * 8) / 1000
                    speed_kbps = int((total_bytes * 8) / 1000 / elapsed)
                    return speed_kbps
                return None