nternals.states.has('--foo'));
        assert_equals(getComputedStyle(myCE).getPropertyValue('color'), 'rgb(255, 0, 0)');
        assert_equals(getComputedStyle(myCE2).getPropertyValue('color'), 'rgb(0, 255, 0)');
        assert_equals(getComputedStyle(mySibling).getPropertyValue('color'), 'rgb(255, 0, 0)');
        assert_equals(getComputedStyle(mySibling2).getPropertyValue('color'), 'rgb(0, 0, 255)');
        myCE.elementInternals.states.clear();
        assert_equals(getComputedStyle(myCE).getPropertyVal