It’s now easy to extend the concept of pairwise or 2-wise test to the generic case of n-wise, with n> 2. The generic Test Set provides n-wise coverage if it is able to cover all the n-tuples (3-tuples if n = 3, 4-tuples if n = 4 and so on). As in the Pairwise, is always possible to know the size of the maximum Test Set, equal to the number n-tuples of values of the variables, but there is no way to know - in the general case - the size of the Test Set Minimum guaranteeing coverage n -wise.
Using NIST Tools (ACTS) or PICT is possible to extract a Test Set that approximates as much as possible the minimum Test Set. It 'clear that, given a set of N variables, the maximum level of wise which you can have is equal to the number of variables. So, if we have 4 variables, a 4-wise test set coincides with all possible combinations, while a 5-wise Test Set or higher makes no sense.