Abstract: A method of determining the functionality of a software system includes inputting a test plan to the software system via a software testing interface program, and logging an indication of one or more resulting outputs of the software system compared to expected output(s). The test plan invokes a sequence of test scripts and includes associated parameter inputs for the test scripts, and an expected output of the function or transaction of each test script. The test scripts are selected from a set of test scripts each able, when input to the software system via a software testing interface program, to prompt performance of a transaction or function for which the software system is designed.