Space} r 0 b / alpha)`,                `color(${colorSpace} 0.7 0 0.3 / 0.4)`);
        test_valid_value(`color`, `color(from color(${colorSpace} 0.7 0.5 0.3 / 40%) ${colorSpace} r g 0 / alpha)`,                `color(${colorSpace} 0.7 0.5 0 / 0.4)`);
        test_valid_value(`color`, `color(from color(${colorSpace} 0.7 0.5 0.3 / 40%) ${colorSpace} r g b / 0)`,                    `color(${colorSpace} 0.7 0.5 0.3 / 0)`);

        // Testing replacement with a constant.
        test_valid_value(`color`, `colo