Added testing with index

[dadrasarmin]

Address this: #262

All credits to copilot. Tested by me on diamond locally.

[bernt-matthias]

Thanks for the effort. Can you add a test case?

[dadrasarmin]

Thanks. I did nothing myself. Honestly, I do not know how to create a test case.

[bernt-matthias]

Maybe you can start from here https://github.com/galaxyproject/planemo/blob/master/tests/test_cmd_test.py, we just need a running command using your new argument and an assertion that ony 1 test was executed

[mvdbeek]

I can add the test if that's too much work / you're busy with something else @dadrasarmin.

[dadrasarmin]

Thank you Marius for taking this over.