So what you are saying is that we can only observe phenomena? Isn't "god" as a label to what caused that phenomenon therefore unnecessary?
Not at all. I'm saying that testing is inherently one-sided. Statisticians call this the problem of confirming or accepting the null hypothesis -- basically, no amount of testing can demonstrate something NOT to exist; it can only provide extremely low bounds on its likelihood and/or effectiveness.
In the case of a test for omnipotence, the "null hypothesis" would be that no limitations exist on the entity's power. Any failure on the entity's part would therefore be evidence against the null hypothesis and give us grounds to reject the idea that it is omnipotent. If it passes that test, then it may or may not be omnipotent; we simply know that it had the power to accomplish THAT task.
How would you know what it is, and how to communicate with it?
You're the one who's producing an entity for me to test. That's your problem, not mine.

