Internal quality evolution of a large test system – an industrial study

This paper presents our empirical observations related to the evolution of a large automated test system. The system observed is used in the industry as a test tool for complex telecommunication systems, itself consisting of more than one million lines of source code. This study evaluates how different changes during the development have changed the number of observed Code Smells in the test system. We have monitored the development of the test scripts and measured the code quality characteristics over a five years period.

The observations show that the introduction of continuous integration, the existence of tool support for quality improvements in itself, changing the development methodologies (from waterfall to agile), changing technical and line management structure and personnel caused no measurable change in the trends of the observed Code Smells. Internal quality improvements were achieved mainly by individuals intrinsic motivation. Our measurements show similarities with earlier results on software systems evolutions presented by Lehman.