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

Jest's setupFiles is the proper way to handle this, and you need not install dotenv, nor use an .env file at all, to make it work.

jest.config.js:

module.exports = {
  setupFiles: ["/.jest/setEnvVars.js"]
};

.jest/setEnvVars.js:

process.env.MY_CUSTOM_TEST_ENV_VAR = 'foo'

That's it.