, 0)`);
    test_valid_value(`color`, `rgb(from rgb(none none none / none) r g b / alpha)`,             `rgba(0, 0, 0, 0)`);
    test_valid_value(`color`, `rgb(from rgb(20% none 60%) r g b)`,                              `rgb(51, 0, 153)`);
    test_valid_value(`color`, `rgb(from rgb(20% 40% 60% / none) r g b / alpha)`,                `rgba(51, 102, 153, 0)`);


    // hsl(from ...)

    // Testing no modifications.
    test_valid_value(`color`, `hsl(from rebeccapurple h s l)`, `rgb(102, 51, 153)`);
    tes