Prevent "test/expect/etc is not defined" errors when using Jest

Question

Facebook's Jest testing framework is easy to get started with, but the documentation overlooks an annoying aspect: test statements will be highlighted as errors by any editor that tries to warn of undefined symbols, because test, expect, and all matcher methods are not defined.

Similary, attempting to run a test file with node directly will fail with ReferenceError: test is not defined.

What require/import statement(s) need to be added for those errors to go away?

Apidcloud · Accepted Answer · 2017-06-20T10:02:30.140

49

Node

~~If you want to run them directly through node, try to require jest and/or jest-runtime.~~ Also give @types/jest a try as well.

Check Edit 2 for new info about this

Edit

@types/jest (jest-DefinitelyTyped) is definitely needed (or just one solution). If you install it (e.g., dev dependency), the IDE errors should go away. I just tried it on Webstorm, and it works.

Edit 2

The new Jest@20 Matchers (e.g., .resolves and .rejects) are still not defined in @types/jest. You can keep track of its status on the links below: https://github.com/DefinitelyTyped/DefinitelyTyped/pull/16645 https://github.com/DefinitelyTyped/DefinitelyTyped/issues/16803

It should be available soon, though!

Also, it doesn't seem possible to run it directly through node. Last night I tried a bunch of different things, but using jest is the way to go - it really uses node under the hood, so I thought it would be possible as well. @thymikee over your opened issue at GitHub made clear that it's not.

Edit 3

The new release (20.0.1) includes the newest Jest definitions.

Lint

this isn't in the scope of this specific problem, but it also helps

Are you using something like ESLint? If so, you'll need eslint-plugin-jest

Following the steps described in this page: https://www.npmjs.com/package/eslint-plugin-jest, you will basically need to add it as an ESLint plugin and set jest globals in the ESLint configuration:

{
  "env": {
    "jest/globals": true
  }
}

If you plan on supporting ES6 tests, you'll also need Babel and babel-jest plugin with the following jest configuration:

"transform": {
  "^.+\\.js$": "babel-jest"
}

Finally, for Typescript tests you'd need the @types/jest and ts-jest packages as well

edited Jun 20 '17 at 10:02

answered Jun 11 '17 at 00:13

Apidcloud

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I use WebStorm actually (ESLint on its own, extending the `google` preset, doesn't even bother to report undefined symbols - you can have `bogusfunc(foo)` in your code and it won't report it), and WebStorm underlines `expect` statements even after adding and configuring `eslint-plugin-jest`. Also, running eslint with or without the plugin says nothing about `test` or `expect` being (un)defined. Not using TypeScript, just ES6. – Dan Dascalescu Jun 11 '17 at 03:03
1

Try to install @types/jest either way. It worked for me on webstorm. Visual studio code also points test and expect to the typescript definitions. – Apidcloud Jun 11 '17 at 03:18
1

Or if you really don't want it as a dev dependency, add it as a webstorm library: File - Languages - JavaScript - libraries - download - and under typescript search for jest-DefinitelyTyped – Apidcloud Jun 11 '17 at 03:20
Adding that WebStorm library fixed `test`, `describe`, `expect` and the matchers, but `rejects` is still underlined as `Unresolved variable` . Adding `jest-matchers-DefinitelyTyped` didn't fix that either. – Dan Dascalescu Jun 11 '17 at 06:46
1

I run into that issue the other day while using Typescript, and found that those new Jest@20 Matchers are still not defined in `@types/jest`. Going to update the answer with some links – Apidcloud Jun 11 '17 at 12:23
The new @types/jest release (**20.0.1**) includes the newest Jest definitions. – Apidcloud Jun 20 '17 at 10:02
2

Thank you so much for mentioning `eslint-plugin-jest`. Although the setup instructions related to `env` and `transform` did not work for me, the vanilla setup instructions at https://www.npmjs.com/package/eslint-plugin-jest did. – Cameron Hudson Jan 31 '20 at 22:03

score 43 · Answer 2 · answered Dec 12 '19 at 06:30

43

Adding following .eslintrc configuration is enough

{"env": 
  {
    "jest": true
  }
}

answered Dec 12 '19 at 06:30

Akshay Vijay Jain

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Perfect & sweet :) (with jest 24.9.0 & eslint 6.8.0) – burntsugar Jan 15 '20 at 03:09
1

Or if you have `eslintConfig` defined in package.json, append this to the "env" settings also works – Junji Zhi Nov 14 '20 at 15:32

score 31 · Answer 3 · answered Mar 15 '18 at 12:48

31

I'm using VSCode and ESLint, you need to install eslint-plugin-jest

Add jest info to your .eslintrc.js

{
  "plugins": ["jest"]
},
"env": {
  "jest/globals": true
}

answered Mar 15 '18 at 12:48

onmyway133

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simply correct with jest 28 ty – Reza Babaei May 26 '22 at 06:32

Prevent "test/expect/etc is not defined" errors when using Jest

3 Answers3

Node

Lint