Three automatic test case generation algorithms intended to test the resource allocation mechanisms of telecommunications software systems are introduced. Although these techniques were specifically designed for testing telecommunications software, they can be used to generate test cases for any software system that is modelable by a Markov chain provided operational profile data can either be collected or estimated. These algorithms have been used successfully to perform load testing for several real industrial software systems. Experience generating test suites for five such systems is presented. Early experience with the algorithms indicate that they are highly effective at detecting subtle faults that would have been likely to be missed if load testing had been done in the more traditional way, using hand-crafted test cases. A domain-based reliability measure is applied to systems after the load testing algorithms have been used to generate test data. Data are presented for the same five industrial telecommunications systems in order to track the reliability as a function of the degree of system degradation experienced. >