Dominators, super blocks, and program coverage

In this paper we present techniques to find subsets of nodes of a flowgraph that satisfy the following property: A test set that exercises all nodes in a subset exercises all nodes in the flowgraph. Analogous techniques to find subsets of edges are also proposed. These techniques may be used to significantly reduce the cost of coverage testing of programs. A notion of a super block consisting of one or more basic blocks in that super block must be exercised by the same input. Dominator relationships among super blocks are used to identify a subset of the super blocks whose coverage implies that of all super blocks and, in turn, that of all basic blocks. Experiments with eight systems in the range of 1-75K lines of code show that, on the average, test cases targeted to cover just 29% of the basic blocks and 32% of the branches ensure 100% block and branch coverage, respectively.