Importing images breaks jest test

问题

In React components importing assets (ex, import logo from "../../../assets/img/logo.png) gives such error

({"Object.":function(module,exports,require,__dirname,__filename,global,jest){�PNG
SyntaxError: Invalid or unexpected token at ScriptTransformer._transformAndBuildScript (node_modules/jest-runtime/build/script_transformer.js:305:17)

my jest config is

"jest": {
"testRegex": ".*\\.spec\\.js$",
"moduleFileExtensions": [
  "js",
  "jsx",
  "json"
],
"moduleDirectories": [
  "node_modules",
  "src",
  "assets"
],
"moduleNameMapper": {
  "\\.(jpg|jpeg|png|gif|eot|otf|webp|svg|ttf|woff|woff2|mp4|webm|wav|mp3|m4a|aac|oga)$/": "<rootDir>/__mocks__/fileMock.js",
  "\\.(css|less|scss)$": "<rootDir>/__mocks__/styleMock.js"
},
"verbose": true,
"bail": true
}

what am i missing?

回答1:

When you import image files, Jest tries to interpret the binary codes of the images as .js, hence runs into errors.

the only way out is to mock a default response anytime jest sees an image import

How do we do this?

first you tell Jest to run the mock file each time an image import is encountered. you do this by adding the key below to your package.json file

"jest": {
 "moduleNameMapper": {
      "\\.(jpg|ico|jpeg|png|gif|eot|otf|webp|svg|ttf|woff|woff2|mp4|webm|wav|mp3|m4a|aac|oga)$": "<rootDir>/__mocks__/fileMock.js",
      "\\.(css|less)$": "<rootDir>/mocks/fileMock.js"
    }
}

if you already have the "Jest" key, just add the "moduleNameMapper" child in it

lastly, create a mocks folder in your root and create fileMock.js file inside it. populate the file with the snippet below

module.exports = ''; 

Note > if you are using es6 you can use export default ''; to avoid an Eslint flag

when you are done with the above steps, you can restart the test and you are good to go.

Note. remember to add the varying extensions of your image files in the moduleNameMapper so that they can be mocked.

I hope I have been able to help. #cheers!

回答2:

If you want to use jest with webpack, you need to explicitly configure it as so. Take a look at this guide here: http://facebook.github.io/jest/docs/en/webpack.html

回答3:

In case of IOS image names with @

moduleNameMapper: {
    "^image![a-zA-Z0-9$_-]+$": "GlobalImageStub",
    "^[@./a-zA-Z0-9$_-]+\\.(png|gif)$": "RelativeImageStub"
  }

来源：https://stackoverflow.com/questions/46898638/importing-images-breaks-jest-test

标签

reactjs

testing

Webpack

jestjs