you might be interested to try to use PC^2 with external validator which submits to an online judge. Basically, you don't need to have test data for a problem, just point to a problem on online judge.
I used it to setup small practice contests for a couple of teams. (When test data is not available.)
In case you are not familiar with PC^2: http://www.ecs.csus.edu/pc2/
Comments / bugs are welcome.