Given that Mar's atmosphere masses about 25 terratonnes compared to Earth's 5148 terratonnes, and Mar's atmospheric pressure is about 1% that of Earth's sea level, you'd need to do high altitude testing at about 30 miles up, which is about 5 Mount Everests.
Much simpler to test fire the engines in a lab somewhere to make sure they run, and test the software in a simulation of the landing. It'll probably come out in the next year or so that there was either just a flat error in the code, or that the simulation was incorrect in some way.
Much simpler to test fire the engines in a lab somewhere to make sure they run, and test the software in a simulation of the landing. It'll probably come out in the next year or so that there was either just a flat error in the code, or that the simulation was incorrect in some way.