Certification trails and software design for testability

This paper investigates design techniques which may be applied to make program testing easier. We present methods for modifying a program to generate additional data which we refer to as a certification trail. This additional data is designed to allow the program output to be checked more quickly and effectively. Certification trails have heretofore been described primarily from a theoretical perspective. In this paper, we report on a comprehensive attempt to assess experimentally the performance and overall value of the certification trail method. The method has been applied to nine fundamental, well-known algorithms for the following problems: convex hull, sorting, huffman tree, shortest path, closest pair, line segment intersection, longest increasing subsequence, skyline, and voronoi diagram. Run-time performance data for each of these problems is given, and selected problems are described in more detail. Our results indicate that there are many cases in which certification trails allow for significantly faster overall program execution time than a two-version programming approach, and also give further evidence of the breadth of applicability of this method