Functions unit test

1. Test if the function correctly calculates the sum of two numbers.

2. Test if the function correctly returns the factorial of a number.
3. Test if the function correctly checks if a number is prime.
4. Test if the function correctly converts Celsius to Fahrenheit.
5. Test if the function correctly sorts a list of numbers in ascending order.
6. Test if the function correctly calculates the area of a circle.
7. Test if the function correctly calculates the volume of a sphere.
8. Test if the function correctly checks if a string is a palindrome.
9. Test if the function correctly calculates the square root of a number.
10. Test if the function correctly generates a Fibonacci sequence up to a certain limit.