Creating a simple unit test

In this recipe, we will introduce unit tests using CTest, the testing tool distributed as a part of CMake. In order to keep the focus on the CMake/CTest aspect and to minimize the cognitive load, we wish to keep the code that is to be tested as simple as possible. Our plan is to write and test code that can sum up integers, and nothing more. Just like in primary school, when we learned multiplication and division after learning how to add, at this point, our example code will only add and will only understand integers; it will not need to deal with floating point numbers. And, just as the young Carl...