title: test input arrays in laravel 5.5 ignore empty or null input values
body: <p>I am currently testing a championship tree with 16 competitors.</p>
  
  <p>Each competitor can be updated via a select combo.</p>
  
  <p>Now, when testing this functionality in Laravel 5.5, I do:</p>
  
  <pre><code>$this-&gt;select([
          $competitor1-&gt;id,
          $competitor2-&gt;id,
          $competitor3-&gt;id,
          $competitor4-&gt;id,
          $competitor5-&gt;id,
  ], 'fighters[]')
          -&gt;press('update');
  </code></pre>
  
  <p>that will put a value on the 5 first combos.</p>
  
  <p>Now, If I try to insert a <code>null</code>, or a <code>""</code> , it is ignored and removed from the select method, so I can only test the first entries, I cannot test the first and the fourth only for example.</p>
  
  <p>Is it something I am not doing properly?</p>