Support jest globalSetup

[DuskLoop]

Is this a bug report?

No

Problem

I have some setup code that I want to run once before all tests. If I run the code in setupTests.js it will run before every test which slows down the total test time alot.

Jest seems to have an option for this: https://facebook.github.io/jest/docs/en/configuration.html#globalsetup-string
But when I add this option in my package.json jest config section I get message:
These options in your package.json Jest configuration are not currently supported by Create React App:

• globalSetup

Would be nice to see this option supported by Create React App or if someone could provide a workaround for this issue.

[Stupidism]

@DuskLoop I think react-app-rewired can help you modifying jest config without ejecting

[gaearon]

Maybe it would be sufficient to use a global flag in src/setupTest.js?

if (!global.initializedTests) {
  // do something
  global.initializedTests = true;
}

I'm not 100% sure but I think global variables should persist between tests.

[DuskLoop]

@gaearon global does not seem to persist between test files.

This code:

if (!global.initializedTests) {
  console.log("doing something");
  global.initializedTests = true;
}

prints for every test file and no difference in performance

[DuskLoop]

@Stupidism I tried running tests with react-app-rewired only to find out that react-scripts currently uses jest 20.0.4, the globalSetup option is supported in jest 22.

Looks like react-scripts is on it's way to update their jest dependency though, the next branch uses version 22.4.1.

[Brian-McBride]

This is an easy change in one file: https://github.com/facebook/create-react-app/blob/master/packages/react-scripts/scripts/utils/createJestConfig.js

Current:

  const supportedKeys = [
    'collectCoverageFrom',
    'coverageReporters',
    'coverageThreshold',
    'resetMocks',
    'resetModules',
    'snapshotSerializers',
    'watchPathIgnorePatterns',
  ];

Changed:

  const supportedKeys = [
    'collectCoverageFrom',
    'coverageReporters',
    'coverageThreshold',
    'globalSetup',
    'globalTeardown',
    'resetMocks',
    'resetModules',
    'snapshotSerializers',
    'watchPathIgnorePatterns',
  ];

One the keys are allowed to pass through, you can just specify these in your package.json jest:{} entry (or wherever).

[gaearon]

That sounds fine to support out of the box. I'll add it.

[pakaplace]

@gaearon , curious as to why certain Jest config options are supported and others are not? I want to use the Jest preset config option, in order to use the jest-puppeteer module with my create-react-app. Could you add it as a supportedKey?

[patricklafrance]

@pakaplace if you customize your CRA with craco you could do it.

Here's a sample craco.config.js file:

module.exports = {
    jest: {
        configure: {
             preset: "jest-puppeteer"
        }
    }
};

Hope this helps!