Should we use react-testing-library or Enzyme? What about snapshot testing? What should be our code coverage? Those are questions we often hear when discussing testing. Those questions are easy to discuss but the answers won’t necessarily make us write more reliable and flexible code. Many developers struggle to write tests 1) quickly and 2) that increase their degree of confidence. Writing good tests requires writing good code. Writing good code that is easy to test requires a good understanding of programming principles and how they apply to the libraries of choice. Discussing principles is harder than discussing tools. In this talk, we’ll discuss the principles that will make developers increase their test confidence when building React apps. I’ll also use those principles to challenge some believes that the audience might have about certain testing libraries or methodologies.