FizzBuzz: creating a byte array from a given number

Implement the method fizzbuzztzest that takes a single integer parameter num and returns a byte array. The array should be formed according to the following rules:

• if the number is divisible by 3 without a remainder — write the string "Fizz";
• if the number is divisible by 5 without a remainder — write the string "Buzz";
• if the number is divisible by both 3 and 5 — write the string "FizzBuzz";
• if the number is not divisible by either 3 or 5 — throw an IllegalArgumentException. Write unit tests covering all behavior scenarios.

public byte[] fizzbuzztzest(int num) {
    throw new Error("Not implemented yet");
}