The KarmaJs for Visual Studio will look for a file named "karma.e2e.conf.js"/"karma.unit.conf.js" in the root directory of your web application project/node.js project. If one is found karma is beeing started. To support proxies (e.g. for AngularJS scenario test) it will also look for a file named server.js (e.g.: https://github.com/karma-runner/karma/blob/master/test/e2e/angular-scenario/server.js).
Code with a running sample: https://github.com/lennybacon/KarmaVS