Specification of a regression test for a mini computer operating system

In this paper I describe the practical problems of designing a regression test set for an existing mini-computer operating system. The ideal regression test would test each function with all possible combinations of the options for each variation of the operating system. This is impractical if not impossible so the alternative is to choose the individual cases for maximum coverage. To do that the system is viewed both functionally and structurally and cases are selected for inclusion in the test set. The method of selecting the tests is described along with the tools that will be needed to measure the coverage and to maintain the test set.