iv.dataset);
  assert_equals(div.dataset.foo, undefined);
}, "Should return 'undefined' before setting an attribute")
test(function() {
  div.setAttribute("data-foo", "value");
  assert_true("foo" in div.dataset);
  assert_equals(div.dataset.foo, "value");
}, "Should return 'value' if that's the value")
test(function() {
  div.setAttribute("data-foo", "");
  assert_true("foo" in div.dataset);
  assert_equals(div.dataset.foo, "");
}, "Should return the empty string if that's the value")
test(function() {
  d