title: How to validate using oneOf with yup
body: <p>I have what I thought was a simple validation using <code>oneOf</code> that isn't working for me with yup:</p>
  <pre class="lang-js prettyprint-override"><code>const schema = Yup.mixed()
    .oneOf([
      {
        error: `EmailOrPasswordInvalid`,
      },
      {},
    ])
    .required();
  </code></pre>
  <p>... later...</p>
  <pre><code>const isValid = schema.isValidSync({ error: `EmailOrPasswordInvalid` });
  console.log(isValid); // false
  </code></pre>
  <p>I'm sure I'm missing something simple but can't put my finger on it. Thanks!</p>