Well, accually a lot of the "expensive testing" can be omitted by doing the paperwork properly. Stress calculations on the type of connections used on model airplanes (usually rods, tubes or flat steel stripes) are very very basic. Calculating a wing rod takes about 5 minutes plus a letter size sheet of paper, plus about 20 minutes research to find the specifications on strength and stiffness of the individual material.
Doing that you can be sure your airframe holds up to your specs, and can test it without having to worry about loosing a plane because of underdimensioned components. Yes it is more work, and yes you have to invest some into someone who is willing to do the math, but all in all that will be cheaper than loosing just a single test airplane. Static load testing will give very realistic results also (to verify calculated numbers).

Best regards
Hank