How to pass arguments to node in Jest tests?

I have tried to use builtin Jest in version 0.3.0 but need to use ES6 Proxy object in test.

This can be done by passing argument --harmony_proxies to node and using harmony-reflect polyfill in test. I am able to import polyfill in tests, but it looks like it's not possible to run jest in node with any additional arguments.

I used to use this in package.json:

  "scripts": {
    "start": "react-scripts start",
    "build": "react-scripts build",
    "eject": "react-scripts eject",
    "test": "node --harmony_proxies node_modules/jest/bin/jest.js"
  }

Now jest is completely under the hood of react-scripts, which is gooood 👍, but how can I pass arguments to node?

I think we should enable --harmony_proxies by default. How can we do this?

@martinschayna

@martinschayna can you upgrade to Node 6 where it is available by default? I don't think we should change how node is invoked; the flags are there for a reason (the feature is experimental in the version of node you are using).

Ah, I didn't realize it just works in Node 6. Let's close then.

For people not using create-react-app and passing by...
I do this in my package.json to pass arguments to Node and Jest (v18.1.0) :

"scripts": {
  "test": "node --trace-warnings node_modules/.bin/jest --no-cache"
}

You can verify that arguments are really treated by passing unknown/bad arguments:

"scripts": {
  "test": "node --bad-node-arg node_modules/.bin/jest"
}

$ yarn test
yarn test v0.20.3
 node --bad-node-arg node_modules/.bin/jest 
node: bad option: --bad-node-arg
error Command failed with exit code 9.

"scripts": {
  "test": "node node_modules/.bin/jest --bad-jest-arg"
}

$ yarn test
yarn test v0.20.3
 node node_modules/.bin/jest --bad-jest-arg 
Unrecognized options: bad-jest-arg, badJestArg

@tkrotoff

@tkrotoff Thank you!

@tkrotoff

@tkrotoff, that doesn't work when passing the --experimental-modules flag to node:

% node --experimental-modules node_modules/.bin/jest
(node:208569) ExperimentalWarning: The ESM module loader is experimental.
 FAIL  ./index.test.mjs
  ● Test suite failed to run

    Jest encountered an unexpected token

    This usually means that you are trying to import a file which Jest cannot parse, e.g. it's not plain JavaScript.

    By default, if Jest sees a Babel config, it will use that to transform your files, ignoring "node_modules".

    Here's what you can do:
[...]
    Details:

    /home/dandv/esmjest/index.test.mjs:1
    ({"Object.<anonymous>":function(module,exports,require,__dirname,__filename,global,jest){import { foo} from './lib';
                                                                                                    ^

    SyntaxError: Unexpected token {

      at ScriptTransformer._transformAndBuildScript (node_modules/jest-runtime/build/script_transformer.js:403:17)

My index.test.mjs has import { foo } from './lib'.

PS: See also overwriting argv.

Navigation Menu

Repository navigation

How to pass arguments to node in Jest tests? #549

Metadata

Assignees

Labels

Type

Projects

Milestone

Relationships

Development

How to pass arguments to node in Jest tests? #549

Description

Activity

gaearon commented on Sep 2, 2016

cpojer commented on Sep 4, 2016

gaearon commented on Sep 4, 2016

tkrotoff commented on Feb 15, 2017

metaskills commented on Jul 18, 2018

dandv commented on Oct 10, 2018

Metadata

Metadata

Assignees

Labels

Type

Projects

Milestone

Relationships

Development

Issue actions