The first tests will be similar to what you're describing, teago, but you don't want to wait until test flying starts to find out your booster needs a major redesign. If you can model it correctly before flying you save a lot of time and money.
Remember that the first time a space shuttle flew into space, it was all on the line, orbiter and crew. While one can argue that this was reckless, it certainly demonstrates the ability to model a complex system very well before it's even flown.