Method of determining effective software testing regions: detection of software defects related to external specification changes

A method of specifying effective testing regions for detecting software defects accompanying changes in external specifications is proposed. On the basis of a careful analysis of actual software defects, the concept of restriction elements is introduced, and it is shown that software defects resulting from external specification changes can be regarded as consisting of the incorrect addition or elimination of these restriction elements. These errors produce a response different from the specifications in certain input regions. A theorem concerning the regions influenced is presented, and examples showing the effectiveness of the method are given