gecko-dev/dom/manifest/test/file_testserver.sjs

"use strict";
Components.utils.import("resource://gre/modules/NetUtil.jsm");
Components.utils.importGlobalProperties(["URLSearchParams"]);

function loadHTMLFromFile(path) {
  // Load the HTML to return in the response from file.
  // Since it's relative to the cwd of the test runner, we start there and
  // append to get to the actual path of the file.
  const testHTMLFile =
    Components.classes["@mozilla.org/file/directory_service;1"].
    getService(Components.interfaces.nsIProperties).
    get("CurWorkD", Components.interfaces.nsIFile);

  const testHTMLFileStream =
    Components.classes["@mozilla.org/network/file-input-stream;1"].
    createInstance(Components.interfaces.nsIFileInputStream);

  path
    .split("/")
    .filter(path => path)
    .reduce((file, path) => {
      testHTMLFile.append(path)
      return testHTMLFile;
    }, testHTMLFile);
  testHTMLFileStream.init(testHTMLFile, -1, 0, 0);
  const isAvailable = testHTMLFileStream.available();
  return NetUtil.readInputStreamToString(testHTMLFileStream, isAvailable);
}

function handleRequest(request, response) {
  const query = new URLSearchParams(request.queryString);

  // avoid confusing cache behaviors
  response.setHeader("Cache-Control", "no-cache", false);

  // Deliver the CSP policy encoded in the URL
  if(query.has("csp")){
    response.setHeader("Content-Security-Policy", query.get("csp"), false);
  }

  // Deliver the CSPRO policy encoded in the URL
  if(query.has("cspro")){
    response.setHeader("Content-Security-Policy-Report-Only", query.get("cspro"), false);
  }

  // Deliver the CORS header in the URL
  if(query.has("cors")){
    response.setHeader("Access-Control-Allow-Origin", query.get("cors"), false);
  }

  // Send HTML to test allowed/blocked behaviors
  response.setHeader("Content-Type", "text/html", false);
  response.write(loadHTMLFromFile(query.get("file")));
}