Exploring Risk-based Testing and Its Implications1

If software cannot be tested exhaustively, it must be tested selectively. But, on what should selection be based in order to maximise test effectiveness? It seems sensible to concentrate on the parts of the software where the risks are greatest, but what risks should be sought and how can they be identified and analysed? 'Risk-based testing' is a term in current use, for example in an accredited test-practitioners' course syllabus, but there is no broadly accepted definition of the phrase and no literature or body of knowledge to underpin the subject implied by it. Moreover, there has so far been no suggestion that it requires an understanding of the subject of risk. This paper examines what is implied by risk-based testing, shows that its practice requires an understanding of risk, and points to the need for research into the topic and the development of a body of knowledge to underpin it.