Determine file system timestamp precision

File timestamps precision is limited to one second for EXT3, one microsecond for UFS, and one nanosecond for EXT4 (at least according to experience). Is there any way to determine this based only on filesystem info? The hacky alternatives I can think of are either to limit all my unit tests to seconds (which I do now), or to touch a bunch of files and checking which digits are zero in stat -c %x.