Why does jest testing break when adding react-router-dom to a react app with create-react-app

Question

I am running a create-react-app with react-16.8.6, and no modifications except for adding react-router to the mix. Now tests don't work.

After rolling things back, I found that the base test fails as soon as I import ANY part of the "react-router-dom" library. Any ideas whats going wrong?

Below is the App.js and App.test.js when I comment out the line:

import { Switch } from "react-router-dom";

the tests run without issue. When I return the line to the code I get the following error:

Test suite failed to run

Cannot find module 'react' from 'react-router-dom.js'

However, Jest was able to find:

'./App.css'
'./App.js'
'./App.test.js'

App.js

import React from "react";
import { Switch } from "react-router-dom";
import logo from "./logo.svg";
import "./App.css";

function App() {
  return (
    <div className="App">
      <header className="App-header">
        <img src={logo} className="App-logo" alt="logo" />
        <p>
          Edit <code>src/App.js</code> and save to reload.
        </p>
        <a
          className="App-link"
          href="https://reactjs.org"
          target="_blank"
          rel="noopener noreferrer"
        >
          Learn React
        </a>
      </header>
    </div>
  );
}

export default App;

app.test.js

import React from "react";
import ReactDOM from "react-dom";
import App from "./App";

it("renders without crashing", () => {
  const div = document.createElement("div");
  ReactDOM.render(<App />, div);
  ReactDOM.unmountComponentAtNode(div);
});

Answer 1

That might be some package manager installation issues. Try to do a fresh install:

rm -rf ./node_modules && rm yarn.lock && yarn

or in case if you're using npm:

rm -rf ./node_modules && rm package-json.lock && npm install

BTW, what is the version of the react-router-dom that you're installing? I've just tried it on the new create-react-app project, installed the latest version of router, but can't reproduce this error ()