title: Jest, React testing a component not exist
body: <p>I have this test:</p>
  <pre><code>const rendered = render(
    &lt;TransactionReason
      reason={{ code: defaultReason }}
    /&gt;
  );
  
  expect(rendered.getByTestId('reasonInput')).toBeNull();
  </code></pre>
  <p>What I'm trying to do is: there is a component that has the <code>testID = 'reasonInput'</code>, but this component is not rendered when the <code>reason</code> prop has that value that I'm giving (code: defaultReason). But I get an error because Jest can't find that id, of course, is not rendered. I thought that that would produce a false or null value, that's why I tried with <code>toBeNull</code> or <code>toBeFalsy</code> or something like that.</p>
  <p>How could I then test the not existance of that component?</p>