Empirical Study of Inspection and Testing Data at Ericsson , Norway

Inspections and testing represent core techniques to ensure reliable software. Inspections also seem to have a positive effect on predictability, total costs and delivery time. This paper presents a case study of inspections and testing, done at the Ericsson development department outside Oslo in Norway. This department develops and maintains customer-defined services around AXE phone switches, i.e. the functionality around the “star”'' and “square” buttons on house telephones. AXE development at Ericsson world-wide uses a simple, local experience database to record inspections and testing data. Two MSc students from NTNU have been given access to such historical data in 1997 [Marjara97] and 1998 [Skaatevik99]. The results from these two diploma theses constitute the basis for this paper. The paper will study questions such as: – The effectiveness and cost-effectiveness of inspections, – The cost-effectiveness and defect profile of inspection meetings vs. individual reading, – The relation between complexity/modification-rate and defect density, – Whether the defect density for modules can be predicted from inspections for later phases and deliveries. The paper is organized as follows: Section 1 summarizes some relevant parts of the state of the art, especially of inspections. Section 2 first describes the Ericsson context, and Section 3 describes questions and hypotheses for the study. Section 4 describes the organization of the study, and Section 5 presents and discusses the results. Section 6 sums up the paper and recommends some future work.