from http.server import BaseHTTPRequestHandler, HTTPServer
from threading import Thread
from urllib.request import urlopen
class Handler(BaseHTTPRequestHandler):
    def do_GET(self):
        self.send_response(200)
        self.send_header("Content-Type", "text/plain; charset=utf-8")
        self.send_header("X-Content-Type-Options", "nosniff")
        self.send_header("Content-Security-Policy", "default-src 'none'; frame-ancestors 'none'")
        self.end_headers()
        self.wfile.write(b"fixture")
    def log_message(self, *args):
        pass
server = HTTPServer(("127.0.0.1", 0), Handler)
thread = Thread(target=server.serve_forever, daemon=True)
thread.start()
try:
    with urlopen(f"http://127.0.0.1:{server.server_port}/", timeout=3) as response:
        assert response.read() == b"fixture"
        assert response.headers["X-Content-Type-Options"] == "nosniff"
        assert "frame-ancestors 'none'" in response.headers["Content-Security-Policy"]
    print("loopback response headers verified")
finally:
    server.shutdown()
    server.server_close()
    thread.join(timeout=3)