This article describes our experience with test suites and automated branch coverage tools for APL software maintenance, based on our use of them to verify Y2K compliance of an APL-based database system. We introduce egregion, a simple, easy-to-use tool that assesses branch coverage in APL functions. The tool comprises a pair of APL functions that report detailed and summary function-level information about code coverage of test suites. The egregion tool provides a line-by-line analysis of statement coverage, labels not branched to, branches never taken, branches always taken, transfer of control via non-branches, and branches to non-labeled lines. Although we do not consider this groundbreaking work, we do believe that the coverage tool will be valuable to APL programmers who are engaged in the creation of large, reliable applications.

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