Testing the features of a product is precise job. But for testing all features of a product, serially executing all tests is not enough. As the Braidy Tester explains, any experienced tester knows that the interaction between features is where the gnarly and deadly bugs hang out. Therefore, testing combinations of features (Cross-feature testing) is important stuff.
But it can be hard to know where to start. The Braidy tester explains he uses pairwise testing as a technique for covering a large test matrix with a smallish number of tests. And extensive guide to pairwise testing can be found at Michael Bolton’s site.