A Metric for Testing Program Verification Systems Bernhard Beckert, Thorsten Bormer, and Markus Wagner The correctness of program verifiation systems is of great importance, and it needs to be checked and demonstrated to users and certifiation agencies. One of the contributing factors to the correctness of the whole verification system is the correctness of the background axiomatization, respectively the correctness of calculus rules. In this paper, we examine how testing verification systems is able to provide evidence for the correctness of the rule base or the axiomatization. For this, we present a new coverage criterion called axiomatization coverage, which allows to judge the quality of existing test suites for verification systems. We evaluate this coverage criterion at two veri cation tools using the test suites provided by each tool.