title: How to find the reason for a risky test in PHPUnit
body: <p>From time to time I get a risky test in PHPUnit. Usually I can find the reason for a risky test. But the task can be time consuming, because I do not see any messages from PHPUnit, why a test is marked as risky. I only get something like this:</p>
  
  <pre><code>PHPUnit 4.4.5 by Sebastian Bergmann.
  
  Configuration read from phpunit.xml.dist
  
  R...................R.R...
  
  Time: 11,91 seconds, Memory: 42,50Mb
  
  OK, but incomplete, skipped, or risky tests!
  Tests: 26, Assertions: 32, Risky: 3.        
  </code></pre>
  
  <p>Is there any option to tell PHPUnit to show messages or better something like stack traces to the code causing the risky flag?
  A complete list of causes for a risky test might prove helpful, too.</p>