When you first learn to code, no one ever starts with writing tests. This means that for many developers, having tests in the code is an afterthought—a luxury if time permits. But what they don't realize is that everyone tests their code, consciously or otherwise.
After you've written a function, how do you know it works? You may open the browser console and run the function with some dummy test parameters, and if the output matches your expectations, then you may assume it's working. But what you're doing here is actually manually testing a function that has already been implemented.
The advantage of manual testing is that it requires no upfront costs—you just run the function and see if it works. However, the downside ...
