  It is a conundrum that agile projects can succeed 'without requirements' when
weak requirements engineering is a known cause for project failures. While
Agile development projects often manage well without extensive requirements
documentation, test cases are commonly used as requirements. We have
investigated this agile practice at three companies in order to understand how
test cases can fill the role of requirements. We performed a case study based
on twelve interviews performed in a previous study. The findings include a
range of benefits and challenges in using test cases for eliciting, validating,
verifying, tracing and managing requirements. In addition, we identified three
scenarios for applying the practice, namely as a mature practice, as a de facto
practice and as part of an agile transition. The findings provide insights into
how the role of requirements may be met in agile development including
challenges to consider.
