A method of testing changes to externalized rules is provided. The method comprises using a rules change management engine and receiving from it a test request for a rules change for a rule. Further, the method comprises providing regression test buckets for testing a version of a rule against each of a plurality of exploiting systems that exploits the rule, and determining for the test request for the rules change received, which of the regression test buckets should be executed against which of the plurality of exploiting systems that exploits the rule and running, using a test rules management system, the regression test buckets that are determined should be executed. The method further comprises reporting results of the regression test buckets that are run to the rules change management engine, such that the rules change management engine is able to determine whether or not to implement the rules change.