add_task(function* () {
  let loadedPromise = BrowserTestUtils.browserLoaded(gBrowser.selectedBrowser, true);
  const htmlContent = "data:text/html, <iframe src='data:text/html,text text'></iframe>";
  gBrowser.loadURI(htmlContent);
  yield loadedPromise;

  yield ContentTask.spawn(gBrowser.selectedBrowser, { }, function* (arg) {
    let frame = content.frames[0];
    let sel = frame.getSelection();
    let range = frame.document.createRange();
    let tn = frame.document.body.childNodes[0];
    range.setStart(tn, 4);
    range.setEnd(tn, 5);
    sel.addRange(range);
    frame.focus();
  });

  let contentAreaContextMenu = document.getElementById("contentAreaContextMenu");

  let popupShownPromise = BrowserTestUtils.waitForEvent(contentAreaContextMenu, "popupshown");
  yield BrowserTestUtils.synthesizeMouse("frame", 5, 5,
        { type: "contextmenu", button: 2}, gBrowser.selectedBrowser);
  yield popupShownPromise;

  ok(document.getElementById("frame-sep").hidden, "'frame-sep' should be hidden if the selection contains only spaces");

  let popupHiddenPromise = BrowserTestUtils.waitForEvent(contentAreaContextMenu, "popuphidden");
  contentAreaContextMenu.hidePopup();
  yield popupHiddenPromise;
});