Find classpath maven is using for running testng testcase

what options to maven can I use to determine what classpath maven is running a testng test case with?

What is the classpath in Maven project?

The reported classpath consists of references to JAR files cached in local Maven repository. Even the JAR artifact of the project is referenced from local Maven cache and not from the /target directory one or the other might expect.

You didn't provide the Maven version, but at least in 3.x (and maybe also 2.x) you can run commands with the -X (debug) option. That way the Test Classpath is printed out before tests are run.