The IRAF/STSDAS program calwf3, which is used to calibrate WFC3 images, has been subjected to a rigorous testing campaign. The operation of each individual calibration step for WFC3 UVIS and IR images has been tested, as well as the ability of the overall calwf3 infrastructure to handle certain error conditions. Several identified problem areas have been corrected and included in the public release of calwf3 version 1.4.