How to Setup Dotenv Globally with Jest Testing

Summary

The article provides a guide on setting up Dotenv globally for Jest testing in a Node.js Express project to avoid manually loading environment variables in each test file.

Abstract

The author of the article encountered an issue where environment variables were not loaded in their Jest tests for a Node.js Express project. Initially, they manually included require('dotenv').config() at the beginning of each test file, which proved to be inconvenient and redundant. Seeking a more efficient solution, the author explored and found a method to load environment variables globally using Jest's setupFiles configuration. The article offers a step-by-step guide to configure a jest.config.js file to automatically load environment variables before running tests, thus eliminating the need to include the Dotenv configuration in every test file. The author also provides an in-depth explanation of how setupFiles work in Jest and shares a real-world example through a GitHub repository branch.

Opinions

The author finds manually including Dotenv configuration in each test file to be a painful and redundant effort.
They positively evaluate the setupFiles feature in Jest for its ability to streamline the environment variable loading process.
The author suggests that the Dotenv library offers multiple ways to expose its APIs to accommodate different user needs.
They imply that the global setup approach for Dotenv with Jest is more efficient and less error-prone than the manual method.

How to Setup Dotenv Globally with Jest Testing — In-depth Explanation

When I am writing unit test for my Nodejs Express project, I realized the configuration I needed is not loaded as environment variables, which we usually access via process.env.VARIABLE_NAME.

I started out by writing require('dotenv').config() on the first line of the test file before all the tests started.

This post is originally published on my blog.

Step by Step Guide

Firstly, createjest.config.js at your project directory.

Add the following code into your jest.config.js.

3. Running Jest Test now can read all your environment variable without writing require('dotenv').config() in each of the test file.

That’s all you need to load the environment variable before you run your test. We will have an in-depth explanation of how the setupFiles work at next section.

In-depth Explanation on Jest config ‘setupFiles’

Prior before we running every test file, we will be running all the path that declare in setupFiles.

In this example, we are equivalent doing require('dotenv/config'). This is equivalent to doing require('dotenv').config().

Thus, we’re running the same function. Ultimately, I think dotenv library provides multiple ways to expose their APIs to handle different needs.

For complete source code on how I set it up, you can refer to this branch.

How to Setup Dotenv Globally with Jest Testing — In-depth Explanation

Disadvantages of this Approach

Can We Setup It Once Globally Before Running the Test?

Step by Step Guide

In-depth Explanation on Jest config ‘setupFiles’

References