[vex]

There's a poor mans compression test, it's not accurate, but it might give you a digital reading of either the engine is blown or not, but not if it's got low compression.

With the car warm: Remove EGI fuse, have friend hold accelerator down, pull leading plug on one rotor, listen for 3 even large pulses. If the engine is not significantly warm (as in you're not shooting out hot air or fluids from the spark plug) you can put your hand close to the spark plug hole and feel the pulses to judge the strength of the seals. Repeat for the other rotor.

With the car cold (will not be as accurate for when it is warm): do the same as above but put your finger over the spark plug hole and make a seal. have your friend crank it. If your finger comes off the hole with the pressure, you have okay compression. If it does not, you do not have good compression on that rotor. (your finger should come off 3 times per orbit of the rotor).

Disclaimer: These tests are significantly inaccurate and will only allow you to know if your engine is blown/not blown. See Teds post for more information