a(153, 94, 51, 0.8)`);
    test_valid_value(`color`, `hsl(from rgb(20%, 40%, 60%, 80%) h 20% l / alpha)`, `rgba(82, 102, 122, 0.8)`);
    test_valid_value(`color`, `hsl(from rgb(20%, 40%, 60%, 80%) h s 20% / alpha)`, `rgba(25, 51, 77, 0.8)`);
    test_valid_value(`color`, `hsl(from rgb(20%, 40%, 60%, 80%) h s l / .2)`, `rgba(51, 102, 153, 0.2)`);

    // Testing valid permutation (types match).
    test_valid_value(`color`, `hsl(from rebeccapurple h l s)`, `rgb(128, 77, 179)`);
    test_valid_value(`color`,