How do I test next/link using Jest? I get an error in Link.prefetch

[jcollum]

• [x ] I have searched the issues of this repository and believe that this is not a duplicate.

Expected Behavior

Links can be used in tests that are run with Jest.

Current Behavior

 at throwIfNoRouter (node_modules/next/dist/lib/router/index.js:107:11)
      at Object.SingletonRouter.(anonymous function) [as prefetch] (node_modules/next/dist/lib/router/index.js:69:5)
      at Link.prefetch (node_modules/next/dist/lib/link.js:143:24)
      at Link.componentDidMount (node_modules/next/dist/lib/link.js:148:12)
      at commitLifeCycles (node_modules/react-dom/cjs/react-dom.development.js:8770:24)
      at commitAllLifeCycles (node_modules/react-dom/cjs/react-dom.development.js:9946:9)

Steps to Reproduce (for bugs)

1. "next": "^5.0.1-canary.15",

2. Create a component with a render method like that returns: (partial):

import Link from 'next/link';
...
render() {
...
    return (
<h3>{messages.LABEL}</h3>
            <ul>
              <li>
                <Link prefetch href={messages.LINK1_URL || ''}>
                  <a>{messages.LINK1_LABEL || ''}</a>
                </Link>
              </li>
              <li>

3.

import React from 'react';
import Enzyme from 'enzyme';
import Adapter from 'enzyme-adapter-react-16';
import enzymify from 'expect-enzyme';
import IndexPage from '../../pages/index';

const {shallow, mount} = Enzyme;
Enzyme.configure({adapter: new Adapter()});

describe('Index', () => {
  it('Renders', () => {
    const messages = {
        LABEL: 'Maguffin'
    };

    const indexPage = mount(
      <IndexPage
        country="us"
        language="en"
        path="/"
        messageBases={messages}
      />
    );

4. jest -t Index

Context

I'm trying to write a Jest test for a page that has a next/link on it.

Your Environment

Tech	Version
next	^5.0.1-canary.15
node	9
OS	OSX 10.12
browser	n/a
etc

[TomiTakussaari]

I've been using something like this to avoid that error:

jest.mock("next/link", () => {
    return ({children}) => {
        return children;
    }
});

Not sure if it would be feasible for next to detect that process.env = "test", and skip prefetch ?

[jcollum]

So I added

import * as jest from 'jest';

jest.mock("next/link", () => {
  return ({children}) => {
    return children;
  }
});

before my describe call and that fixed it.

Thanks so much!