b(153, 51, 255)`);
    test_valid_value(`color`, `hwb(from rebeccapurple h w b / 0)`, `rgba(102, 51, 153, 0)`);
    test_valid_value(`color`, `hwb(from rgb(20%, 40%, 60%, 80%) 0 w b / alpha)`, `rgba(153, 51, 51, 0.8)`);
    test_valid_value(`color`, `hwb(from rgb(20%, 40%, 60%, 80%) 0deg w b / alpha)`, `rgba(153, 51, 51, 0.8)`);
    test_valid_value(`color`, `hwb(from rgb(20%, 40%, 60%, 80%) h 0% b / alpha)`, `rgba(0, 77, 153, 0.8)`);
    test_valid_value(`color`, `hwb(from rgb(20%, 40%, 60%, 80%) h w 0% / 