Next.js: publicRuntimeConfig undefined in test environment with Jest.

[YIZHUANG]

Bug report

When unit testing a utility function that needs access to the publicRuntimeConfig with jest, it throws error Cannot read property 'publicRuntimeConfig' of undefined

Describe the bug

For example if i am testing a file that has Contentful stuff in it, and the access token those kind of stuff comes from publicRuntimeConfig, then the test won't past and shows above error.

To Reproduce

// next.config.js

module.exports = () => {
  return {
    publicRuntimeConfig: {
      accessToken: '1234565',
    }
  };
};

// util.js

import getConfig from 'next/config'
const { publicRuntimeConfig } = getConfig()
const client = createClient({
   accessToken: publicRuntimeConfig.accessToken
})
function mathCaculation(){
  return 1+1
}

util.test.js

expect(mathCaculation()).toBe(2)

Cannot read property 'publicRuntimeConfig' of undefined

System information

"next": "^7.0.2",

[timneutkens]

Duplicate of #4024

Specifically: https://github.com/zeit/next.js/issues/4024#issuecomment-386016077

[damusnet]

Hi all,

I think I have a different solution/explanation. I too was hit by tests not passing anymore when upgrading from Next.js 7 to 8.

Previously I had a Jest mock in __mocks__/next/config.js. However, it looks to me like even though we do import getConfig from 'next/config', the mock must now be at __mocks__/next-server/config.js. Not entirely quite sure yet why, or what changed recently, but this at least fixes it for me.

The same is true for __mocks__/next/dynamic.js which is now __mocks__/next-server/dynamic.js.

It also applies if you used to do jest.mock('next/config', () => () => ({ publicRuntimeConfig: { ... } })); for instance.

But I think it makes sense:

Maybe the docs should be updated to reflect the new structure and have import getConfig from 'next-server/config'?

[gabrieledarrigo]

@damusnet I occurred into the same problem, thank you so much for spotting this!
@timneutkens should this be documented?

[timneutkens]

This is something we can solve on the Next.js side of things I think 🤔