When it comes to studying for lucid dreaming, the test you're studying for is the dream, and the test is on what a dream is. You're being tested on identifying the test. During the dream, you'll likely have less access to memory, so it will be more difficult to know you're being tested in the first place because it will be more difficult to remember what the test is. If during the dream you recall you're being test, you still have to remember what you learned about what a dream is.

Also, it's more difficult to learn what a dream is because it can take on so many forms. Sort of like an octopus! Say you were diving and were told "avoid the octopus, you'll get inked! You know what an octopus looks like, right? Well identify the octopus in the picture below.


Spoiler for solution:


Other than those couple of quibbles, I like the analogy of studying for the test of the dream by learning about and intending to remember what dreams are like.