This build step expects to be executed in a job started by an "Execute TPT test cases" build step in master mode. The master job will provide some parameters used by this build step. It will execute excatly one test case and copies the result back to the master node. To execute a single test case the build step uses the TPT RMI API. The Job should be only run once on every Computer. You can achive that e.g. by Throttle Concurrent Builds Plugin