title: Configuring Cypress, cypress-react-unit-test, and React
body: <p>I want to test our React components independently using the package <code>cypress-react-unit-test</code>. After several days, I have been unable to get it to work with the existing React Webpack configuration.
  I get the error: <code>TypeError: path argument is required to res.sendFile</code> when I open the file through Cypress' window.</p>
  
  <p>I am using the file from their example repo for testing: 
  <a href="https://github.com/cypress-io/cypress-example-recipes/blob/master/examples/unit-testing__react/greeting.jsx" rel="noreferrer">https://github.com/cypress-io/cypress-example-recipes/blob/master/examples/unit-testing__react/greeting.jsx</a></p>
  
  <p>We do use TypeScript, but I wanted to get this working first.</p>
  
  <p>I have tried overwriting <code>path</code> as it is defaulting to <code>undefined</code>, but I'm getting the same error.</p>
  
  <pre><code>{
    options: {
      path: "/my/home/dir/"
    }
  }
  </code></pre>
  
  <p>In my <code>cypress/plugins/index.js</code> file I have:</p>
  
  <pre><code>const wp = require("@cypress/webpack-preprocessor");
  
  const webpackConfig = require("../../node_modules/react-scripts/config/webpack.config")("development");
  
  module.exports = on =&gt; {
    const options = {
      webpackOptions: webpackConfig
    };
  
    on("file:preprocessor", wp(options));
  };
  </code></pre>
  
  <p>I'm obviously missing something, but I don't know Webpack well enough. I would be grateful for any pointers! Thanks!</p>