How can we know if a dharma teaching is really what the Buddha taught? Is there some sort of test?

It seems that there are different "versions" of Buddhism today, and many of the teachings from these different versions appear to be at odds with one another. I'd like a way to tell which teachings are incomplete, corrupted, or flat-out fakes. If Buddhism is really a "science" of the mind, like many teachers say, shouldn't there be ways to test things? Are there ways to test the authenticity of a teaching?