test return value of transaction

Question

contractA

function test() internal {
  stateVariable = 20;
  uint num = 20;
  assembly {
     mstore(0x00, num)
     return(0x00, 0x20)
  }
}

How do I test the return ? I am using hardhat , but i don't think it changes anything.

Step 1: I should create another contract contractB which is a mock and which is the child of the contractA. This way, I can make this contractB's function public and it will include the internal function - test.

After this, I'd appreciate if I could hear your opinions what could be the best way to make sure to test this.