NLP is an interesting parallel example. Its founders believed in testing, but the students, not so much. For example, Bandler, in "Using Your Brain For A Change", wrote:

A mathematician doesn't just get an answer and say, "OK, I'm done." He tests his answers carefully, because if he doesn't, other mathematicians will! That kind of rigor has always been missing from therapy and education. People try something and then do a two-year follow-up study to find out if it worked or not. If you test rigorously, you can find out what a technique works for and what it doesn't work for, and you can find out right away. And where you find out that it doesn't work, you need to try some other technology.

It's a transcript from a lecture demonstration where he's just shown how to extinguish someone's urge to smoke, and is testing the result. The volunteer had just claimed she no longer wished to smoke, but Bandler insists that she actually take a cigarette from him, hold it in her hands, and play around with it.

He says:

When you do change work, don't back away from testing it; push it. Events in the world are going to push it, so you may as well do it so you can find out right away. That way you can do something about it. Observing your client's nonverbal responses will give you much more information than the verbal answers to your questions.

He then points out the changed facial expression on the volunteer -- it appears that smelling the cigarette has restored her desire for one. He gives her some modified instructions, to repeat the technique being taught. Afterwards, they verify that the smell no longer acts as a compulsion trigger.

Now, the crazy thing is, Bandler's been teaching this stuff for 20 years, but hardly anybody "gets it"... about testing, or damn near anything else.

Few NLP practitioners do much testing; few NLP books even mention it. Even Bandler's own books don't say that much about it. The formal NLP trainings emphasize "outcome frame" (defining in advance what result you're trying to get), but not so much the process of testing that you've achieved that outcome.

I suspect that this is simply because Bandler is a lousy teacher in some ways. In my personal experience, the most important parts of nearly every Bandler video, audio, or book are in what seem like almost offhand remarks... that happen to reveal volumes if you already happen to be close to figuring out the same thing for yourself. Perhaps this is why he's so insistent that an NLP certification is worthless if it doesn't come from him.