tenfourfox/toolkit/mozapps/extensions/test/xpinstall/browser_enabled.js

// ----------------------------------------------------------------------------
// Test whether an InstallTrigger.enabled is working
function test() {
  waitForExplicitFinish();

  gBrowser.selectedTab = gBrowser.addTab();

  ContentTask.spawn(gBrowser.selectedBrowser, TESTROOT + "enabled.html", function (url) {
    return new Promise(resolve => {
      function page_loaded() {
        content.removeEventListener("PageLoaded", page_loaded, false);
        resolve(content.document.getElementById("enabled").textContent);
      }

      function load_listener() {
        removeEventListener("load", load_listener, true);
        content.addEventListener("PageLoaded", page_loaded, false);
      }

      addEventListener("load", load_listener, true);

      content.location.href = url;
    });
  }).then(text => {
    is(text, "true", "installTrigger should have been enabled");
    gBrowser.removeCurrentTab();
    finish();
  });
}