Avoiding manual tests

Instead, you should formally define these manual tests as code, in the form of unit, integration and end-to-end (E2E) tests, among others.

Formally defining tests has a higher initial cost, but the benefit is that the tests can now be automated. As we will cover in Chapter 5, Writing End-to-End Tests, once a test is defined as code, we can use npm scripts to run it automatically every time the code changes, making the cost to run the tests in the future virtually zero.

The truth is that you'll need to test your code anyways; it's just a choice of whether you invest time to automate it now, saving time in the future, or save the time now but waste more time repeating each test manually in the future.

Mike Cohn developed the concept of the Testing Pyramid, which shows that an application should have a lot of unit tests (as they are fast and cheap to run), fewer integration tests, and even fewer UI tests, which take the most amount of time and are the most expensive to define and run. Needless to say, manual testing should only be done after unit, integration, and UI tests have been thoroughly defined: