rom lch(0.7 45 30 / 40%) l c 0deg / alpha)`, `lch(0.7 45 0 / 0.4)`);
    test_valid_value(`color`, `lch(from lch(0.7 45 30 / 40%) l c h / 0)`, `lch(0.7 45 30 / 0)`);

    // Testing replacement with a constant.
    test_valid_value(`color`, `lch(from lch(0.7 45 30) 25 c h / alpha)`, `lch(25 45 30)`);
    test_valid_value(`color`, `lch(from lch(0.7 45 30) l 25 h / alpha)`, `lch(0.7 25 30)`);
    test_valid_value(`color`, `lch(from lch(0.7 45 30) l c 25 / alpha)`, `lch(0.7 45 25)`);
    test_valid_value(`colo