Challenge 1: Find the Greatest Common Divisor

Problem Statement

Implement a function that takes two numbers, testVariable1 and testVariable2 and returns their greatest common divisor.

What is the Greatest Common Divisor?

The Greatest Common Divisor of two or more integers is the largest positive integer that divides each of the integers.

For example, take two numbers $42$ and $56$.

$42$ can be completely divided by $1$ ...