example.js

function next(ms) {
  if (win["about:buildconfig"]) {
    asserts.forEach(function(fn) {
      fn(test, win);
    });
    done();
  } else if (ms >= 0) {
    setTimeout(next, 500, ms - 500);
  } else {
    assert.fail("about:buildconfig page-mod to be executed");
  }
}(ms);