title: Set System propery to Null in Java
body: <p>In my unit tests I need to set the "workingDir" system property to Null.</p>
  
  <p>But I can not do somesing like this, because It give me NullPointerException:</p>
  
  <pre><code>System.setProperty("workingDir", null);
  </code></pre>
  
  <p>How can I do it?</p>