sert_equals(getComputedStyle(mySibling).getPropertyValue('color'), 'rgb(255, 0, 0)');
        assert_equals(getComputedStyle(mySibling2).getPropertyValue('color'), 'rgb(255, 0, 0)');
        myCE.elementInternals.states.add('--green');
        assert_true(myCE.elementInternals.states.has('--green'));
        assert_equals(getComputedStyle(myCE).getPropertyValue('color'), 'rgb(255, 0, 0)');
        assert_equals(getComputedStyle(myCE2).getPropertyValue('color'), 'rgb(255, 0, 0)');
        assert_equals(getCo