answer:#2 doesn’t make sense, because the training doesn’t test the product, it’s the skills learned while being trained that help us when we test the product. #1 The same problem as #2, it is a bit confusing if the training will be testing the product, or helping the people that are testing the product. #3 is right because it has a preposition tied to a gerund. The in is not redundant, it preposes the subject as using the training in the process of testing.