It took my some time to figure out that under the "Program to execute" I had to enter my test engine. In my case mstest.exe, or nunit.exe.
However I have the feeling the arguments textbox can only hold one argument, not multiple. For example when I specify a .vsmdi file where my test-lists are configured, I can't add another parameter with /testlist:"integration tests" for example. I get all kinds of errors, where a single parameter does work.
Perhaps a "Test assembly" or "Test Metadata file" textbox where I can enter a .dll or .vsmdi file (like in the "Run MSTest" action) would be wonderfull. And please still allow the "Arguments" or "Additional parameters" option.
We’re a bit short staffed at the moment (we are recruiting, it’s just proving difficult to find the right people) so it may take us longer to respond than is usual for us… in this case you have a work around so that put’s it lower on the todo list. We will get to this either today or tomorrow.