I had to create multiple file upload user interface for an old style asp.net web forms app. I know... old technology but what can you do when a system which is created 8 years ago is still working and you have to support it till the new version win MVC 4.0 eventually starts.
For that task I used one very nice jQuery plugin made by blueimp. It is very nice and works for most of the browsers ... who supports IE9... :) anyway in order to test the upload of large files I had create some with particular size equal to the exact maximum possible upload size.
For that reason I used cmd tool
Below is a screenshot showing an example of the execution of the program: