publicRuntimeConfig undefined in test environment with Jest.

Bug report

TypeError: Cannot read property ‘CMS_URL’ of undefined

Describe the bug

when I call service in getInitialProps

class IndexService {
  getPage(lang = 'en') {
    return axios
      .get(
        `${publicRuntimeConfig.CMS_URL}

A clear and concise description of what the bug is.

To Reproduce

I have jest.config.js as

module.exports = {
  setupFiles: ['./jest.setup.js'],
  testPathIgnorePatterns: ['./.next/', './node_modules/'],
  moduleNameMapper: {
    "^.+\\.(css|less|scss)$": "babel-jest"
  },
};

I have jest.setup.js as

import { configure } from 'enzyme'
import Adapter from 'enzyme-adapter-react-16'
import { setConfig } from 'next/config'
import config from './next.config'

// Make sure you can use "publicRuntimeConfig" within tests.
setConfig(config.publicRuntimeConfig)
configure({ adapter: new Adapter() })

Steps to reproduce the behavior, please provide code snippets or a repository:

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4. See error

Expected behavior

The thing is when I call a service class from other files as indexService I got this error

Screenshots

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System information

• Version of Next.js: 9

Additional context

Add any other context about the problem here.

[Harrisonkamau]

In my case, I mocked the next/config as shown:

// jest.setup.js
jest.mock('next/config', () => () => ({
  publicRuntimeConfig: { // put test stuff here },
}));

Then call it in your jest.config.js - I did this so it can run in every component. If you don’t like this behavior, then mock the next/config inside of the component you’re testing.

module.exports = {
 setupFiles: ['./jest.setup.js'],
};

[kachkaev]

@ShintaroNippon if you’re using any plugins in next.config.js, there is a chance that its default export will be a function, not an object. Therefore, config.publicRuntimeConfig will be undefined.

Try console.log(config) in your jestSetup.js. If you don’t see any logs at all, your jest setup file is not invoked – that’s a separate issue, solved via jest docs. If you see a printed function in the output, try the following:

import { setConfig } from "next/config"
import generateNextConfig from "./next.config"
// or
// import * as generateNextConfig from "./next.config"

// Make sure you can use "publicRuntimeConfig" within tests
setConfig({
  publicRuntimeConfig: generateNextConfig("", {}).publicRuntimeConfig,
})