How do I save a value in global in Jest during test setup?

Question

I have a global setup in Jest.

"jest": {
    "globalSetup": "./setup.js"
  }

Within the setup, I have an async function which writes a session key to global

const axios = require('axios');

async function getSessionKey() {
    const response = await axios.post("http://apiUrl", {
        username: "K",
        password: "passw0rd"
    });
    sessionKey = response.data.sessionKey;
    global.sessionKey = sessionKey;
}

module.exports = getSessionKey;

Whatever session key I am saving in global is not available in the test file. global.sessionKey is undefined in the below test.

test("create session", () => {
    expect(global.sessionKey).toBeTruthy();
});

I want some way to set the sessionKey in a global object from setup file. The session key should be available before I run any of my tests.

Possibly a bug with Jest - https://github.com/facebook/jest/issues/5424. For now, I replaced Jest with Mocha in my project and everything is good! — vijayst, Jan 30 '18 at 17:05

score 6 · Accepted Answer · edited Jan 12 '22 at 20:41

6

globalSetup/globalTeardown can't be used to inject context/global variables to sandboxed test suites/files. Use setupFiles/setupFilesAfterEnv instead.

Other way you can customize the test runtime through testEnvironment, more details see here: Async setup of environment with Jest

edited Jan 12 '22 at 20:41

cdoublev

709
6
18

answered Jan 30 '18 at 21:41

Allen

4,431
2
27
39

2

how should I use the `setupFiles`? it says in the docs that I can add this as a field in package.json in jest subfields, but it only says it should be an array and that the default value is `[ ]`. so what should I do if I want to add for instance, a `jest.setTimeout(10000);` config there? – ganjim Sep 10 '18 at 13:06

score 3 · Answer 2 · edited Oct 01 '19 at 04:57

I spend a lot of time figuring this out right. The only fully working solution was using testenvironments. This supports async functions as well as globals properly. Each test suite uses a separate instance of the testenvironment.

const NodeEnvironment = require('jest-environment-node');

class TestEnvironment extends NodeEnvironment {
  constructor(config) {
    super(config);
  }

  async setup() {
    await super.setup();
    this.global.db = await asyncCode();
  }

  async teardown() {
    this.global.db = null;
    await asyncCode2();
    await super.teardown();
  }

  runScript(script) {
    return super.runScript(script);
  }
}

module.exports = TestEnvironment;

I added a reference to this file in the Jest Config: "testEnvironment": "./testEnvironment" for the file testEnvironment.js

I'm not sure though why there are so many different config options like setupFiles, globals, testEnvironment, ...

This runs per test suite and can't share memory between instances. It's basically like beforeAll and afterAll hooks. — José Cabo, Dec 14 '19 at 17:30

score 3 · Answer 3 · answered Dec 23 '19 at 17:51

3

Setting an env variable like process.env.SESSION_KEY = sessionKey from globalSetup seems to work for me in subsequent tests.

I can access the value properly from any test. Not sure if this is a bug or a feature.

answered Dec 23 '19 at 17:51

andreialecu

3,639
3
28
36

It’s between a bug and a feature. I use it since it’s pretty much the only meaningful way to communicate between Jest setup and tests. There’s supposed to be a proper feature for passing serializable data from setup to tests, and once that is out, the env way may be closed. – akauppi Jul 16 '21 at 18:23

How do I save a value in global in Jest during test setup?

3 Answers3