Interesting craft in that it's essentially just a larger version of the R/C toys you can buy. I wonder how they tested the blade design. Did they fly it at 100,000ft on Earth?
Obviously it wouldn't be able to fly in the pressure chamber due to increased gravity, but by suspending it on elastic you can still test that the blade functions as intended.
The only bit you can't really fully test is the constants for the control loops in the flight control algorithm, but I assume they chose them with a lot of stability margin.
They did exactly that. NASA has a big (adjustable) vacuum chamber for this kind of purpose.
This comment links to video: https://news.ycombinator.com/item?id=28432811