Write a Python script that prompts the user to input a number, and then determines if the number is a Fibonacci number or not. The script should output "Yes" if the number is a Fibonacci number, and "No" if it is not. The script should be well-documented, readable, and follow PEP 8 style guidelines. In addition, the script should use a function to calculate whether the number is a Fibonacci number or not, and the function should be unit tested.
This prompt doesn't seem malicious.