");
  var children_inner = fs_inner.elements;
  assert_array_equals(children_inner, [fm1.querySelector("[name=txt_inner]")],
                      "The items in the collection must be children of the inner fieldset element.");
  assert_array_equals(children_outer, [fm1.querySelector("[name=cb]"), fm1.querySelector("[name=txt]"), fm1.querySelector("[name=btn]"), fm1.querySelector("#fs_inner"), fm1.querySelector("[name=txt_inner]")],
                      "The items in the collection must be children of the o