  assert_true(expected instanceof CSSUnitValue);
    assert_equals(actual.value, expected.value);
    assert_equals(actual.unit, expected.unit);
  }

  test(() => {
    assert_unit_value(target.computedStyleMap().get('left'), CSS.px(30));
    assert_unit_value(target.computedStyleMap().get('top'), CSS.px(50));
    assert_unit_value(target.computedStyleMap().get('width'), CSS.px(20));
    assert_unit_value(target.computedStyleMap().get('height'), CSS.px(40));
  }, 'Effects of position-try-fallbacks are visib