The development of large, software-intensive systems is a complex undertaking that is generally tackled by a divide and conquer strategy. Organizations face thereby the challenge of coordinating the resources which enable the individual aspects of software development, commonly solved by adopting a particular process model. The alignment between requirements engineering (RE) and software testing (ST) activities is of particular interest as those two aspects are intrinsically connected: requirements are an expression of user/customer needs while testing increases the likelihood that those needs are actually satisfied.

The work in this thesis is driven by empirical problem identification, analysis and solution development towards two main objectives. The first is to develop an understanding of RE and ST alignment challenges and characteristics. Building this foundation is a necessary step that facilitates the second objective, the development of solutions relevant and scalable to industry practice that improve REST alignment.

The research methods employed to work towards these objectives are primarily empirical. Case study research is used to elicit data from practitioners while technical action research and field experiments are conducted to validate the developed  solutions in practice.

This thesis contains four main contributions: (1) An in-depth study on REST alignment challenges and practices encountered in industry. (2) A conceptual framework in the form of a taxonomy providing constructs that further our understanding of REST alignment. The taxonomy is operationalized in an assessment framework, REST-bench (3), that was designed to be lightweight and can be applied as a postmortem in closing development projects. (4) An extensive investigation into the potential of information retrieval techniques to improve test coverage, a common REST alignment challenge, resulting in a solution prototype, risk-based testing supported by topic models (RiTTM).

REST-bench has been validated in five cases and has shown to be efficient and effective in identifying improvement opportunities in the coordination of RE and ST. Most of the concepts operationalized from the REST taxonomy were found to be useful, validating the conceptual framework. RiTTM, on the other hand, was validated in a single case experiment where it has shown great potential, in particular by identifying test cases that were originally overlooked by expert test engineers, improving effectively test coverage.