Often, not all test cases are included in a test.

[Kiriru777]

Say, this can be very possible situation, tossed variants are: 1 3 2 3 1 2 3 2 1 2 3. The test has no variants for 4 and 5. Maybe implement two wariants of tests: 1) even distrubution of all possible variants; and 2) completely free distribution of variants?

[Gdalik]

Thanks for the suggestion!
What about the more difficult patterns where there are more (sometimes much more) variants than questions within one test? And for the simpler ones, I do not like the idea that a student can calculate what options are left instead of just using his/her ears. The only condition that I made was the exclusion of two identical options in the consequent examples.

[Kiriru777]

I guess, there could be different paths:

1. tests are form of learning. In that case, repetition is the way.
2. tests are form of attestation. In that case total randomness is the way.