title: PhpStorm: "Run with coverage" results in "Cannot load Xdebug - extension already loaded"
body: <p>I just upgraded my PhpStorm project from PHPUnit 4.x to PHPUnit 5.x. Running my unit tests works fine.</p>
  
  <p>In order to get "run with coverage" working, I had to edit my Run/Debug configuration and add <code>--whitelist=/path/to/whitelisted/dir</code> to Test Runner options. Now coverage is generated when I choose "Run with coverage," but I get this Xdebug warning.</p>
  
  <pre><code>Testing started at 12:06 PM ...
  /usr/local/opt/php56/bin/php -dzend_extension=/usr/local/opt/php56-
  xdebug/xdebug.so -dxdebug.coverage_enable=1 
  /Users/bwood/code/php/WpsConsole/vendor/phpunit/phpunit/phpunit --
  whitelist=/Users/bwood/code/php/WpsConsole/src --coverage-clover /Users/bwood/Library/Caches/PhpStorm2017.3/coverage/WpsConsole$NEW.coverage --no-configuration /Users/bwood/code/php/WpsConsole/tests/UnitTests --teamcity
  
  Cannot load Xdebug - extension already loaded
  PHPUnit 5.7.27 by Sebastian Bergmann and contributors.
  </code></pre>
  
  <p>I think the issue is that php is being called with </p>
  
  <pre><code>-dzend_extension=/usr/local/opt/php56-xdebug/xdebug.so
  </code></pre>
  
  <p>But I can't figure out where I can remove that option. I'm testing a console application so there is no webserver configuration.</p>