SUMMARY
The principles of imitation model for knowledge test control, specifically on the perfection of the procedure of constructing a test, are developed in this model. The authors suggest taking into account the difficulty of the question when one is making a decision about including a given test question into the test. They also suggest using iterational calculations in order to create a test with the help of optimization algorithms that are used for the process of random searching. The sum of task complexity indices for such test will meet the criteria of joint value and difficulty. Detailed explanation of mathematical apparatus that is used for decision-making during the test-building process is given in the article as well as an example that demonstrates main steps of iterational calculations and mechanisms for achieving optimal test structure based on the criteria of joint value and difficulty.