d_value(`color`, `hsl(from rgb(20%, 40%, 60%, 80%) h 0% l / alpha)`, `rgba(102, 102, 102, 0.8)`);
    test_valid_value(`color`, `hsl(from rgb(20%, 40%, 60%, 80%) h s 0% / alpha)`, `rgba(0, 0, 0, 0.8)`);
    test_valid_value(`color`, `hsl(from rgb(20%, 40%, 60%, 80%) h s l / 0)`, `rgba(51, 102, 153, 0)`);

    // Testing replacement with a constant.
    test_valid_value(`color`, `hsl(from rebeccapurple 25 s l / alpha)`, `rgb(153, 94, 51)`);
    test_valid_value(`color`, `hsl(from rebeccapurple 25deg s l / al