What's most important for this particular certification -- that people learn something that is useful or that they prove they can regurgitate information from memory?

Speaking from the slide of test tool, there are various techniques to minimize cheating, from basic to advanced.
1. Time Limit
Put a time limit on the test so that test takers have not time to guess.

2. Randomization
Always randomize questions when test takers view the test every time. In this way, memorizing answers becomes difficult.

3. Question Bank
You create a large question bank and only use some of them randomly for a test taker.
That means every test taker should have different questions to take.

4. Access Control
You can set up accounts and password and assign these accounts to the test takers.
When they use the accounts to login to the test, these info will be checked.
This is to limit the access and only user expected can take the test.

5. Disable Multiple Attempts
This is the way to disallow user from taking the test for more than one time.
The first attempt will be recorded as cookies in the end user PC and any refreshing is not workable because it is locked.

Possibly there are other methods against cheating.

Or you may like to look at how these features work in a test tool at here.