test process.env with Jest

Question

I have an app that depends on environmental variables like:

const APP_PORT = process.env.APP_PORT || 8080;

and I would like to test that fo

Answer 1

You can use setupFiles feature of jest config. As documentation said that,

A list of paths to modules that run some code to configure or set up the testing environment. Each setupFile will be run once per test file. Since every test runs in its own environment, these scripts will be executed in the testing environment immediately before executing the test code itself.

1. npm install dotenv dotenv that uses to access env variable.
2. Create your .env file to root directory of your application and add this line into it.

#.env
APP_PORT=8080

3. Create your custom module file as It name being someModuleForTest.js and add this line into it.

//someModuleForTest.js
require("dotenv").config()

4. Update your jest.config.js file like this

module.exports = {
  setupFiles: ["./someModuleForTest"]
}

5. You can access env's variable within all test blocks.

test("Some test name", () => {
  expect(process.env.APP_PORT).toBe("8080")
})