rom rgb(20%, 40%, 60%, 80%) h l l / l)`, `rgba(61, 102, 143, 0.4)`);
    test_valid_value(`color`, `hsl(from rgb(20%, 40%, 60%, 80%) h alpha alpha / alpha)`, `rgba(163, 204, 245, 0.8)`);

    // Testing with calc().
    test_valid_value(`color`, `hsl(from rebeccapurple calc(h) calc(s) calc(l))`, `rgb(102, 51, 153)`);
    test_valid_value(`color`, `hsl(from rgb(20%, 40%, 60%, 80%) calc(h) calc(s) calc(l) / calc(alpha))`, `rgba(51, 102, 153, 0.8)`);

    // Testing with 'none'.
    test_valid_value(`color`, `