Pairwise Testing

http://www.pairwise.org/tools.asp 

Pairwise Testing Combinatorial Test Case Generation

Pairwise (a.k.a. all-pairs) testing is an effective test case generation technique that is based on the observation that most faults are caused by interactions of at most two factors. Pairwise-generated test suites cover all combinations of two therefore are much smaller than exhaustive ones yet still very effective in finding defects.