r(from color(${colorSpace} 0.7 0.5 0.3 / 40%) ${colorSpace} r g none / alpha)`,             `color(${colorSpace} 0.7 0.5 none / 0.4)`);
        test_valid_value(`color`, `color(from color(${colorSpace} 0.7 0.5 0.3 / 40%) ${colorSpace} r g b / none)`,                 `color(${colorSpace} 0.7 0.5 0.3 / none)`);
        // FIXME: Clarify with spec editors if 'none' should pass through to the constants.
        test_valid_value(`color`, `color(from color(${colorSpace} none none none) ${colorSpace} r g b)`,     