add_task(async function () {
  // create mocked objects
  let launcher = createMockedObjects(true);

  // open helper app dialog with mocked launcher
  let dlg = await openHelperAppDialog(launcher);

  let doc = dlg.document;
  let dialogElement = doc.getElementById("unknownContentType");

  // Set remember choice
  ok(
    !doc.getElementById("rememberChoice").checked,
    "Remember choice checkbox should be not checked."
  );
  doc.getElementById("rememberChoice").checked = true;

  // Make sure the mock handler information is not in nsIHandlerService
  ok(
    !gHandlerSvc.exists(launcher.MIMEInfo),
    "Should not be in nsIHandlerService."
  );

  // close the dialog by pushing the ok button.
  let dialogClosedPromise = BrowserTestUtils.windowClosed(dlg);
  // Make sure the ok button is enabled, since the ok button might be disabled by
  // EnableDelayHelper mechanism. Please refer the detailed
  // https://searchfox.org/mozilla-central/source/toolkit/components/prompts/src/PromptUtils.sys.mjs#51
  dialogElement.getButton("accept").disabled = false;
  dialogElement.acceptDialog();
  await dialogClosedPromise;

  // check the mocked handler information is saved in nsIHandlerService
  ok(gHandlerSvc.exists(launcher.MIMEInfo), "Should be in nsIHandlerService.");
  // check the extension.
  var mimeType = gHandlerSvc.getTypeFromExtension("abc");
  is(mimeType, launcher.MIMEInfo.type, "Got correct mime type.");
  for (let handlerInfo of gHandlerSvc.enumerate()) {
    if (handlerInfo.type == launcher.MIMEInfo.type) {
      // check the alwaysAskBeforeHandling
      ok(
        !handlerInfo.alwaysAskBeforeHandling,
        "Should turn off the always ask."
      );
      // check the preferredApplicationHandler
      ok(
        handlerInfo.preferredApplicationHandler.equals(
          launcher.MIMEInfo.preferredApplicationHandler
        ),
        "Should be equal to the mockedHandlerApp."
      );
      // check the perferredAction
      is(
        handlerInfo.preferredAction,
        launcher.MIMEInfo.preferredAction,
        "Should be equal to Ci.nsIHandlerInfo.useHelperApp."
      );
      break;
    }
  }
});