I don't think that having to specify the number of zeroes is too problematic--testing a string formatting routine means guaranteeing a specific output.

I oftentimes feel that `%f`'s output is a little bit verbose, though. If you used `%g`, it would strip all "unnecessary" zeroes--`10.52` -> `10.52`, but `10.50` -> `10,5` and `10.0` -> `10`--and that might be a bit more common-sensical as far as reading and testing the output.