Only display the expected value after student has attempted koan

[DavidWhitlock]

Hey, @matyb and all. My students this summer used the koans in my Java programming course and I got an interesting piece of feedback about them: Because the expected value of the "__" is always displayed before attempting to solve the koan, it was very tempting for the students to simply paste the expected value into the assertion statement and move on.

What would be the feasibility of displaying the expected result only after the student has attempted the koan once (or twice or whatever you think makes sense)?

So, information such as

What went wrong: 
expected:<true> but was:<REPLACE ME>

would not be displayed until the koan has already failed once.