title: System clear Property doesn't work. How can it be?
body: <p>I really don't understand!</p>
  
  <p>I run unit tests which contains cod:</p>
  
  <pre><code>  String progDir = "prog.dir";
    System.clearProperty(progDir);
    System.out.println(System.getProperty(progDir));
  </code></pre>
  
  <p>And on console I see prog dir path. Although there must be null.</p>
  
  <p>I setting this variable in setUp block. This is junit test. This variable need for all other test but not for that, so I tried to clean it in the start of this test method. If I remove setting of this  var from setUp block this test will pass.</p>
  
  <p>System.setProperty work fine.</p>
  
  <p>How can it be?
  Thanx</p>