Using Acceptance Tests for Incremental Elicitation of Variability in Requirements: An Observational Study

Variability in software systems refers to the notion that the components constituting the software may vary due to a range of factors including diverse customer needs, technical constraints, and business strategies. Traditionally, variability has been treated proactively by investing in an upfront domain analysis phase. Such proactive treatment of requirements is not encouraged in agile environments. This paper provides an observational study examining a reactive approach to variability wherein acceptance tests are used to elicit variability from requirements in an incremental manner. The findings suggest the following: the approach does support the evolutionary nature of agile development, the approach is easy and quick to learn, using acceptance tests yields consistent variability interpretations, and acceptance tests -- on their own -- may be insufficient to reflect implicit variability constraints.