Okay, guys, I think I've figured out what Astro Teacher is trying to say here.
Astrology, according to AT, doesn't deal in predictions. It deals in chances. Essentially, you go to AT, AT says "Hey, this may happen".
It's a very handy system for AT, because he/she is never straight-up wrong. If it DOES happen, then "wow, you're amazing!" If it doesn't, then "well, he said that it only MIGHT happen, so I guess he was right that it might not!"
While it's impossible to disprove, it's also quite a dishonest way of thinking.
If that is all that AT is saying, then it's certainly not beyond testing. Even probabilistic claims can be tested, and are tested often.
In order for the transit to be meaningful, the event in question would need to be more likely to happen than we would expect from chance.
If we can find an experienced astrologer willing to do so, we can have the astrologer tell us that something is more likely than it would usually be, by a certain margin, many times in a row. We can then count the number of successes and failures of the established event, compare the results to chance, and see if the transits appeared to have any actual positive effect on the odds.