Jest: Flow type support?

[aksonov]

I'm trying to use flow syntax within unit tests, but i don't see any way to test it

 - Error: Line 5: Unexpected token :
        at createError (node_modules/jest-cli/node_modules/istanbul/node_modules/esprima/esprima.js:2392:21)
        at unexpectedTokenError (node_modules/jest-cli/node_modules/istanbul/node_modules/esprima/esprima.js:2467:13)
        at throwUnexpectedToken (node_modules/jest-cli/node_modules/istanbul/node_modules/esprima/esprima.js:2472:15)
        at parseClassBody (node_modules/jest-cli/node_modules/istanbul/node_modules/esprima/esprima.js:5045:21)
        at parseClassDeclaration (node_modules/jest-cli/node_modules/istanbul/node_modules/esprima/esprima.js:5067:21)
        at parseStatementListItem (node_modules/jest-cli/node_modules/istanbul/node_modules/esprima/esprima.js:3935:24)
        at parseFunctionSourceElements (node_modules/jest-cli/node_modules/istanbul/node_modules/esprima/esprima.js:4766:23)
        at parseFunctionExpression (node_modules/jest-cli/node_modules/istanbul/node_modules/esprima/esprima.js:4972:16)
        at parsePrimaryExpression (node_modules/jest-cli/node_modules/istanbul/node_modules/esprima/esprima.js:3232:24)
        at inheritCoverGrammar (node_modules/jest-cli/node_modules/istanbul/node_modules/esprima/esprima.js:2648:18)

[cpojer]

I suggest using babel-jest to preprocess your files and strip flow-annotations before tests are being run on them. Follow the guide for React testing on the bottom here: http://facebook.github.io/jest/docs/tutorial-react.html#content

(Note: we are in the process of upgrading babel-jest to babel6. For now I recommend using babel-jest 5 until we have ironed out the issues).

[aksonov]

Thanks, problem was exactly with usage of babel 6 ! Babel-jest 5 works like a charm.

[kevinastone]

@cpojer, that tutorial didn't explain how to install the babel plugin transform-flow-strip-types. Could we add a note?

[cpojer]

I think we should add some notes for this somewhere. cc @hramos.

[thomb]

FWIW Here is the transformer I put together to get jest running with transform-flow-strip-types after npm install --save-dev babel-plugin-transform-flow-strip-types

const babelJest = require('babel-jest');
const jestPreset = require('babel-preset-jest');

module.exports = babelJest.createTransformer({
    plugins: [
        "transform-flow-strip-types"
    ],
    presets: [jestPreset]
});

[hramos]

Ooof, I wasn't aware this was an issue people might need help with. If you still think this should be documented, feel free to open a new issue and assign it to me.

[thomb]

The only reason I commented here (which I now realize was closed, my bad) is the last comment saying "yeah, we should document this!"

[hramos]

Yeah! That is on me to document. Unfortunately it's not been on my mind as the issue is closed.

[thymikee]

@thomb transform-flow-strip-types plugin (or flow preset) just works with Jest when added to your Babel config.

[jsdario]

Hi @thymikee, do you have a sample? I imagine that requires several configurations for prod, dev and testing.

[thymikee]

_.babelrc_

{
  "presets": [
    "flow"
  ]
}

That's all.

[rayrutjes]

Is it exepected that this doesn't work with jest?

export default class {
  urlsToVisit: { [string]: boolean } = {};
}

Error being Unexpected token:

[cpojer]

Flow is supported, if you are getting this error, it's because you didn't properly set up your babel build pipeline.

[rayrutjes]

@cpojer Well I'm using the flow preset, and I think it's an error specific to jest, given it works fine when I just use yarn run flow.

[zsirfs]

@aksonov
Finally, can you tell me how to solve this problem?

[yiakwy]

I am adding a jest feature to unity tests, @thomb, compilation broken. It does not work for me. am I missing anything?

[kaladivo]

I have the same problem as @rayrutjes. Is there any solution to it?