Laravel/PHPUnit: Assert json element exists without defining the value : <p>I'm sending a post request in a test case, and I want to assert that a specific element, let's say with key 'x' exists in the response. In this case, I can't say <code>seeJson(['x' =&gt; whatever]);</code> because the value is unknown to me. and for sure, I can't do it with <code>seeJson(['x']);</code>. </p>

<p>Is there a way to solve this?</p>

<p>If it matters:
Laravel: v5.2.31
PHPUnit: 5.3.4</p>
