I just use the ide junit integration to run the testcase under the debugger. In intellij its available under right click/Debug ...
My goal was to debug a testcase when running in the collection "tests-security-basic-unit". I solved it by directly placing the JPDA block inside the "run-junit" macro, in my local workspace.
For a single test, you can use the target "one-test-debug" which essentially does the same as the way you do in IDEA.