Jest failed to parse a file. This happens e.g. when your code or its dependencies use non-standard JavaScript syntax

Question

I'm using ignite to create an expo react native app. I'm using this guide https://ignitecookbook.com/docs/recipes/GeneratorComponentTests to create component test files

Here is the first test file

import React from "react"
import { fireEvent, render, screen } from "@testing-library/react-native"
import { HelloWorld } from "../HelloWorld"

describe("HelloWorld", () => {
  it("renders", () => {
    render(<HelloWorld />)
    expect(screen.getByText("Hello")).toBeTruthy()
  })
})

I followed https://reactnativetesting.io/component/setup/ in order to install @testing-library/react-native but now I'm getting

 ● Test suite failed to run

    Jest encountered an unexpected token

    Jest failed to parse a file. This happens e.g. when your code or its dependencies use non-standard JavaScript syntax, or when Jest is not configured to support such syntax.

    Out of the box Jest supports Babel, which will be used to transform your files into valid JS based on your Babel configuration.

    By default "node_modules" folder is ignored by transformers.

    Here's what you can do:
     • If you are trying to use ECMAScript Modules, see https://jestjs.io/docs/ecmascript-modules for how to enable it.
     • If you are trying to use TypeScript, see https://jestjs.io/docs/getting-started#using-typescript
     • To have some of your "node_modules" files transformed, you can specify a custom "transformIgnorePatterns" in your config.
     • If you need a custom transformation specify a "transform" option in your config.
     • If you simply want to mock your non-JS modules (e.g. binary assets) you can stub them out with the "moduleNameMapper" config option.

    You'll find more details and examples of these config options in the docs:
    https://jestjs.io/docs/configuration
    For information about custom transformations, see:
    https://jestjs.io/docs/code-transformation

    Details:

    /Users/montylennie/AbutFrontend/app/components/specs/HelloWorld.spec.tsx:12
            (0, react_native_1.render)(<HelloWorld_1.HelloWorld />);
                                       ^

    SyntaxError: Unexpected token '<'

      at Runtime.createScriptFromCode (node_modules/jest-runtime/build/index.js:1518:14)
      at asyncGeneratorStep (node_modules/@babel/runtime/helpers/asyncToGenerator.js:3:24)
      at asyncGeneratorStep (node_modules/@babel/runtime/helpers/asyncToGenerator.js:22:9)

Here is my jest.config.js file

const { defaults: tsjPreset } = require("ts-jest/presets")

/** @type {import('@jest/types').Config.ProjectConfig} */
module.exports = {
  ...tsjPreset,
  preset: "jest-expo",
  transformIgnorePatterns: [
    "<rootDir>/node_modules/(react-clone-referenced-element|@react-native-community|react-navigation|@react-navigation/.*|@unimodules/.*|native-base|react-native-code-push)",
    "jest-runner",
  ],
  testPathIgnorePatterns: ["<rootDir>/node_modules/", "<rootDir>/.maestro/", "@react-native"],
  testEnvironment: "jsdom",
  setupFiles: ["<rootDir>/test/setup.ts"],
  setupFilesAfterEnv: ["<rootDir>/jest-setup-after-env.js"],
}

And here is my contents of jest.config.js

import '@testing-library/jest-native/extend-expect';

What am I missing?

Lyrate

Did you install @testing-library/react-native? – Portland

It's generally frowned on to edit in a way that changes the core question (both are problems with testing with Jest in an Expo-generated app, but different problems). I don't use Expo — did it give you a Babel config? The various config files in this directory are a good reference. – Portland

Answer 1

You have a few problems with your jest.config.js file:

• You are mixing two presets: jest-expo for Expo apps and ts-jest for TypeScript apps. This can cause conflicts or unexpected behavior, because they might have different settings or transformations. You should only use one preset at a time, or use the projects option to separate different sub-projects.
• You are using the transformIgnorePatterns option to tell Babel to ignore some modules. But this option only works for the default transformer, which is babel-jest. If you are using a different transformer, like ts-jest, you need to use the transformerConfig option to pass the ignore patterns to it.
• You are using the testEnvironment option to set jsdom, which is a browser-like environment for testing web apps. But you are testing a React Native app, which is a mobile app that runs on native platforms. You should use the node environment instead, which is the default for Jest. Or you can use the react-native environment, which is provided by the jest-expo preset.

To fix these issues, you need to update your jest.config.js file and choose the right options for your project. For example, if you are testing an Expo app with TypeScript, you could use something like this:

module.exports = {
  preset: "jest-expo",
  transform: {
    "^.+\\.(js|jsx|ts|tsx)$": "ts-jest",
  },
  globals: {
    "ts-jest": {
      transformerConfig: {
        transformIgnorePatterns: [
          "<rootDir>/node_modules/(react-clone-referenced-element|@react-native-community|react-navigation|@react-navigation/.*|@unimodules/.*|native-base|react-native-code-push)",
          "jest-runner",
        ],
      },
    },
  },
  testPathIgnorePatterns: [
    "<rootDir>/node_modules/",
    "<rootDir>/.maestro/",
    "@react-native",
  ],
  testEnvironment: "react-native",
  setupFiles: ["<rootDir>/test/setup.ts"],
  setupFilesAfterEnv: ["<rootDir>/jest-setup-after-env.js"],
};

Hoyt

Define ts-jest config under globals is deprecated. Please do transform: { <transform_regex>: ['ts-jest', { /* ts-jest config goes here in Jest */ }], } – Magnetochemistry

tansform was what i needed for using babel-jest, thanks!! – Filip