1. A method, in a data processing system comprising a processor and a memory, for evaluating test cases for testing a software product based on a requirements change, the method comprising: analyzing, by the data processing system, a test case corpus to identify a plurality of first relationships between elements of test cases in the test case corpus; generating, by the data processing system, a test case relationship model based on the identified plurality of first relationships; receiving, by the data processing system, a proposed requirements change to change one or more requirements of the software product; searching, by the data processing system, the test case relationship model to identify test case relationships corresponding to the proposed requirements change; identifying, by the data processing system, a subset of test cases in the test case corpus affected by the proposed requirements change based on the identified test case relationships corresponding to the proposed requirements change at least by generating a ranked listing that ranks each test case having at least one test case relationship corresponding to the proposed requirements change, relative to other test cases having at least one test case relationship, based on whether the at least one test case relationship associated with the test case is a direct relationship or an indirect relationship, whether the test case has multiple test case relationships corresponding to the proposed requirements change, and whether the at least one test case relationship comprises both a direct relationship and an indirect relationship, and selecting test cases from the ranked listing to be the subset of test cases based on relative rankings of the test cases in the ranked listing; and generating, by the data processing system, an output specifying the identified subset of test cases, wherein, in response to the selected test cases comprising a null set of test cases due to no test cases in the ranked listing having corresponding ranks meeting or exceeding the at least one threshold rank value, the output identifies a test case to be generated to test the software product with regard to the proposed requirements change.