title: Getting failed tests (TypeError) only when running PhantomJS
body: <p><strong>tl;dr</strong> How to remove this error in PhantomJS?</p>
  
  <h1>Repo</h1>
  
  <p>Reference Repo: <a href="https://github.com/Sawtaytoes/Tabletop-Helper/tree/d123927b8f65fc97234fd2543bf9103ac0db58ab" rel="nofollow noreferrer">https://github.com/Sawtaytoes/Tabletop-Helper/tree/d123927b8f65fc97234fd2543bf9103ac0db58ab</a></p>
  
  <p>Run <code>yarn test</code>.</p>
  
  <h1>Issue</h1>
  
  <p>When running these same tests from Chrome vs PhantomJS, I'm seeing errors show up related to the Webpack bundle, or so I thought.</p>
  
  <h1>Error</h1>
  
  <pre><code>TypeError: undefined is not a constructor (evaluating '__WEBPACK_IMPORTED_MODULE_3_content_smash_up_decks__["a" /* sets */].find(function (set) { return title === set.title; })')
  </code></pre>
  
  <h1>Code</h1>
  
  <pre><code>sets
  .find(set =&gt; title === set.title)
  .decks
  .reduce((combined, { title }) =&gt; ({ ...combined, [title]: setState }), {})
  </code></pre>
  
  <h1>Confusion</h1>
  
  <p>The line in particular that's breaking is <code>sets.find()</code>. If I leave that out and make it <code>sets[0]</code>, it works. In logging out the values of <code>sets.find()</code>, it always returned a matching array because the tests are written to pass in a valid set title.</p>
  
  <p>The other two tests that have a similar error are also referencing <code>sets.find()</code>. What it is about this function that that PhantomJS doesn't like?</p>