III 5 - 6 September 2005 Department of Computer Science University of Sheffield

Branch testing, for example, seeks to cover all branches in a piece of code, but when it is performed, as well as branches, other program elements, such as statements or puses, will necessarily be covered. The contemporaneous coverage of these other elements is referred to as “collateral coverage”. An understanding of the extent of the collateral coverage of the various program elements that is afforded by the available testing methods, can be used to determine an optimal deployment of the methods in pursuance of the aim of covering one or more of those elements. In this paper, as a step towards such an understanding, the collateral coverage that branch testing yields in respect of JJ-paths, and that JJ-testing yields in respect of branches, is investigated. The results of the investigation do, in fact, facilitate the definition of a policy for deploying the two methods when branch coverage, JJ-path coverage, and/or both of these is sought. However perhaps surprisingly, they also indicate that the widespread preference for branch over JJ-path testing, may not be justified.