If you are picking up this book, it is because you want to level up the quality of the code you are producing. Regardless of the background and what type of work you are trying to achieve, testing is a prime indicator of solid software practices....
Any programmer working with a dynamically typed language will tell you how hard it is to scale to more lines of code and more engineers. That's why Facebook, Google, and Microsoft invented gradual static type layers for their dynamically typed...