Before starting, it is important to remember the existence of a universe of Formatters and Linters, but I prefer to leave them for an article on standards, where we can talk about the choices that are the reason for which linters exists: reinforce patterns, either by convention, security or whatever technical reasons.

We will talk about:

• Unit
• Integration
• End-to-end
• Regression

Each of these will be structured with:

• What it is
• When to use it
• Pros
• Cons
• Tools

Unit

What it is

As the name says, it refers to the units, and, as the word suggest, it means that it is something that cannot be divided, since it is the smallest possible part. When referring to software, it means that they are functions that only do one thing. Unit tests are responsible for attesting that such functions (or units) are behaving properly. As we are talking about Front-End, these functions are written in Javascript or any other language that compiles to it.

Whether using the TDD process or not, it is difficult for a developer to take into account all possible scenarios, especially when programming such functions. Writing unit tests can help you to prepare your code for situations that are not “optimal”. In addition, they can make sure that during the life of the project, the “little guys” (unit tests) will complain before you notice such errors, in case something goes out of the established format or architecture,. By writing them, you are creating an army of robots with a life of their own, whose only mission is to observe their functions and ensure that they are correct.

An example, in the case of a function that formats dates, would be to guarantee the outputs, for practically all types of input — which happens when someone uses a date in different formats, invalid dates, and so on, including how the function handles errors and exceptions.

#software-development #front-end-development #javascript #testing