);
    test_valid_value(`color`, `lch(from lch(0.7 45 30 / 40%) calc(l) calc(c) calc(h) / calc(alpha))`, `lch(0.7 45 30 / 0.4)`);

    // Testing with 'none'.
    test_valid_value(`color`, `lch(from lch(0.7 45 30) none none none)`,                                   `lch(none none none)`);
    test_valid_value(`color`, `lch(from lch(0.7 45 30) none none none / none)`,                            `lch(none none none / none)`);
    test_valid_value(`color`, `lch(from lch(0.7 45 30) l c none)`,                  