Congratulations on the build. Great feeling on the first one.
To answer your question, the test means that the internals are working fine and that the LE is sending commands out to the TRIACs based on the DMX inputs (as far as the systems knows).
What isn't tested is the actual power going through the TRIAC and switching taking place.
To run a true test of your LE will require to provide power to both sides of the LE and testing each output on each of the 16 outputs to make sure that all of the TRIACs are good.
Speaking from personal experience, sometimes the TRIACs will fail on (in my case, I am almost certain it was poor static electricity defense procedures on my part) when they fail. This means that your lights will stay lit no matter what the LE is sending to the unit to switch. However, I built 6 last year and only had two 'triac' issues. I think that is pretty darn good.
Kurt