title: Compare two XML strings ignoring element order
body: <p>Suppose I have two xml strings</p>
  
  <pre><code>&lt;test&gt;
    &lt;elem&gt;a&lt;/elem&gt;
    &lt;elem&gt;b&lt;/elem&gt;
  &lt;/test&gt;
  
  &lt;test&gt;
    &lt;elem&gt;b&lt;/elem&gt;
    &lt;elem&gt;a&lt;/elem&gt;
  &lt;/test&gt;
  </code></pre>
  
  <p>How to write a test that compares those two strings and ignores the element order?</p>
  
  <p>I want the test to be as short as possible, no place for 10-line XML parsing etc. I'm looking for a simple assertion or something similar.</p>
  
  <p>I have this (which doesn't work)</p>
  
  <pre><code>   Diff diff = XMLUnit.compareXML(expectedString, actualString);   
     XMLAssert.assertXMLEqual("meh", diff, true);
  </code></pre>