Created attachment 33005 [details] TestCellReference.java patch It looks like the org.apache.poi.ss.util.TestCellReference unit test only covers 3 of the constructors, CellReference(String), CellReference(int, int), and formatAsString is not tested for all possible inputs. I've added these two cases to the TestCellReference in the attached patch.
Thanks, patch committed in r1696427.