Exhaustive testing of computer software is intractable, but empirical studies of software failures suggest that testing can in some cases be effectively exhaustive. We show that software failures in a variety of domains were caused by combinations of relatively few conditions. These results have important implications for testing. If all faults in a system can be triggered by a combination of n or fewer parameters, then testing all n-tuples of parameters is effectively equivalent to exhaustive testing, if software behavior is not dependent on complex event sequences and variables have a small set of discrete values.

Software plays an increasing role in the safety critical systems. Increasing the quality and reliability of the software has become the major objective of software development industry. Researchers and industry practitioners, look for innovative techniques and methodologies that could be used to increase their confidence in the software reliability. Fault tree analysis (FTA) is one method under study at the Software Assurance Technology Center (SATC) of NASA's Goddard Space Flight Center to determine its relevance to increasing the quality and the reliability of software. This paper briefly reviews some of the previous research in the area of software fault tree analysis (SFTA). Next we discuss a roadmap for application of the SFTA to software, with special emphasis on object-oriented design. This is followed by a brief discussion of the paradigm for transforming a software design artifact (i.e., sequence diagram) to its corresponding software fault tree. Finally, we discuss challenges, advantages and disadvantages of SFTA.