Understanding different types of test

First, let's learn about the different types of tests and how they all fit into our project's workflow. The first thing to note is that some tests are more technically-focused, while others are more business-focused; some tests are only concerned with a very small part of the whole system, while others test the system as a whole. Here's a brief overview of the most common types of tests you'll encounter:

• Unit tests: These test the smallest testable parts of an application, called units. For example, if we have a function called createUser, we can write a unit test that tests that the function always returns a promise. With unit tests, we are only concerned with the function of the unit, independent of external dependencies. If the unit has external dependencies, such as a database, we must substitute the real database client with a fake one. This fake client must be able to mimic the behavior of the database adequately so that, from the perspective of...