White-Box Path Generation in Recursive Programs

We present an algorithm for generating paths through a set of mutually recursive functions. The algorithm is part of a tool for white-box test-case generation. While in imperative programs there is a well established notion of path depth, this is not the case in recursive programs. We define what we mean by path and path depth in these programs and propose an algorithm which generates all the static paths up to a given depth. When the algorithm is applied to transformed iterative programs, giving as a result tail-recursive functions, the defined depth corresponds to the maximum number of times the loop condition is evaluated. When applied to non-tail recursive functions, the meaning is their maximum unfolding depth along the path, for each initial call to the function. It can also be applied to hybrid programs where both iteration and recursion are present.