In accordance with an embodiment, described herein is a system and method for providing a test manager for use with a mainframe rehosting platform. The test manager can run in a web server and is accessed through a web browser to run testing on multiple test machines. The test manager can be configured to automatically discover test units from a deployed migrated application and its artifacts, and organize the discovered test units into various test plans. The test manager can be used to capture a baseline from an online execution against a mainframe platform at the network data stream layer, and to drive both execution against the rehosting platform and automated comparison of the results. The test manager can further be configured to execute batch jobs against both the mainframe platform and the rehosting platform and compare the results from both platforms, to determine if the batch jobs results match.