You can access object window.__karma__ which has property files. You can iterate over it.
I just entered this code into my test-main.js:
for (var file in window.__karma__.files) {
console.log(file)
}
All served files would be printed to console among other messages. Here is sample from my output:
...
Firefox 32.0.0 (Ubuntu) LOG: '/base/node_modules/requirejs/require.js'
Firefox 32.0.0 (Ubuntu) LOG: '/base/node_modules/karma-requirejs/lib/adapter.js'
Firefox 32.0.0 (Ubuntu) LOG: '/base/node_modules/karma-jasmine/lib/jasmine.js'
...