title: How to ignore .catch promise in code coverage with istanbul?
body: <p>I'm using BluebirdJS promise library and I have <code>.catch</code> that I can't mock that is why I can't cover it with my code coverage using istanbul. </p>
  
  <pre><code>.then(() =&gt; ....)
  /* istanbul ignore next */ -&gt; Does not work
  .catch((err) =&gt; err) /// I want to ignore this
  </code></pre>
  
  <p>Does someone know if this is possible with istanbul library?</p>
  
  <p>Thanks!</p>
  
  <p>EDIT: This is the full code, my test can't reach the <code>.catch</code> because it's always passing and I can't seem to another way to force mongoose to throw an error</p>
  
  <pre><code> const { payload } = request
  
   const group = new LocationGroups(payload)
  
   group.save()
     .then(reply)
     .catch((error) =&gt; reply(boomify(error)))
  </code></pre>