One of Veryant's ISVs uses TestComplete from SmartBear software (http://www.automatedqa.com/products/testcomplete/)
Veryant has experimented with TestComplete and has verified that it can be used successfully with COBOL applications developed with isCOBOL to do functional and regression testing.
With isCOBOL, any of TestComplete's features that are designed for Java or Web applications can be used with COBOL applications as well.
Another resource is Wikipedia's list of GUI testing tools at http://en.wikipedia.org/wiki/List_of_GUI_testing_tools
Any testing tool designed to be used with Java Swing GUI applications can be used to test COBOL GUI applications deployed with isCOBOL. And any testing tool designed for Web applications can be used to test COBOL Web applications deployed with COBOL Servlets, COBOL Web Services or COBOL GUI SCREEN SECTION with isCOBOL Web Direct 2.0.