When you have a very simple application it’s not so important to test every edge case but in a project, in the very complex domain, the priority of it will increase. The more high-quality the tests, the more high-quality the code. Mutational tests will help you with making sure you did not miss some a variant of the flow in your code. How it works Mutational testing is a test which runs other test several times but with a bit changed production code in every iteration.

I’ll tell you a story of Igor. Igor is a web developer. He’s a young man with a girlfriend and some ambitious plan in the future. Igor sit at his desk because he has some work to do. In front of him is a PC. He turns it on and sees some system updates. 30 minutes have passed, and he can see his desktop with a beautiful wallpaper. Funny cats always make his day better.