How Scrum adds value to achieving software quality?

Scrum remains the most popular agile software development method implementation for a variety of reasons; one important motive is to improve software quality. Yet many organizations fail to achieve quality improvements through the use of Scrum, and existing research sheds little light on the value-add of Scrum for software quality. More specifically, (1) how notions of software quality among Scrum practitioners relate to established quality perspectives, (2) how Scrum helps teams to achieve higher software quality and (3) why some teams fail to meet the objective of higher quality. We addressed these gaps through a two-phased qualitative study based on 39 interviews and two in-depth case studies. We find that Scrum practitioners emphasize established notions of external quality comprising of conformity to business needs and absence of defects, while they also value internal quality, especially sustainable software design. Our results show that Scrum helps teams achieve both dimensions of quality by promoting some social antecedents (collaboration, psychological safety, accountability, transparency) and process-induced advantages (iterative development, formal inspection, and adaptation). Our findings unveil how these factors contribute to achieving software quality and under what conditions their effects can fail to materialize. These conditions include inconsistent Scrum implementations, cultural constraints, team tensions, and inaccessibility of end-users. In addition, the complexity of the project aggravates the impact of these conditions. Taken together, these findings show that Scrum can complement established quality assurance and software engineering practices by promoting a social environment that is conducive to creating high-quality software. Based on our findings, we provide specific recommendations for how practitioners can create such an environment.