This is a problem reproduction in Next@6

1. with-jest
2. add some styled-jsx as external style.https://github.com/zeit/styled-jsx#keeping-css-in-separate-files

reproduce steps

1. yarn test

result

● With Enzyme › App shows "Hello world!"

ReferenceError: style is not defined

    2 |
    3 | export default () => (
  > 4 |   <div className='hello'>
    5 |     <p>Hello World</p>
    6 |     <style jsx global>{style}</style>
    7 |   </div>

    at Object._default [as type] (pages/index.js:4:3)
    at Object.<anonymous> (__tests__/index.test.js:11:17)

● With Snapshot Testing › App shows "Hello world!"

ReferenceError: style is not defined



    at _default (pages/index.js:21:10)
    at Object.<anonymous> (__tests__/index.test.js:22:48)

Note:

but yarn dev and yarn build is work fine.