Component Testing Is Not Enough - A Study of Software Faults in Telecom Middleware

The interrelationship between software faults and failures is quite intricate and obtaining a meaningful characterization of it would definitely help the testing community in deciding on efficient and effective test strategies. Towards this objective, we have investigated and classified failures observed in a large complex telecommunication industry middleware system during 20032006. In this paper, we describe the process used in our study for tracking faults from failures along with the details of failure data. We present the distribution and frequency of the failures along with some interesting findings unravelled while analyzing the origins of these failures. Firstly, though “simple” faults happen, together they account for only less than 10%. The majority of faults come from either missing code or path, or superfluous code, which are all faults that manifest themselves for the first time at integration/system level; not at component level. These faults are more frequent in the early versions of the software, and could very well be attributed to the difficulties in comprehending and specifying the context (and adjacent code) and its dependencies well enough, in a large complex system with time to market pressures. This exposes the limitations of component testing in such complex systems and underlines the need for allocating more resources for higher level integration and system