Building Enterprise JavaScript Applications

When implementing a new feature, write your E2E tests first

A common misinterpretation of TDD and the Testing Pyramid is that unit tests are more important than E2E tests, and that you should start writing unit tests first. This is wrong. TDD only requires you to write tests first, but does not specify the type of test you must use. The Testing Pyramid simply encourages you balance your test suite to have more granular tests; it does not specify the importance or order for which you test.

In fact, when implementing a new feature, E2E tests are the most important tests, and should be the first test you write when composing your test suite. E2E tests mimic how your end users would interact with the project, and are often tied to the business ...