fixed Factory to support "/" as the only common path

Author: julianseeger

src/CodeCoverage/Report/Factory.php

@@ -277,6 +277,18 @@ private function reducePaths(&$files)
 
         ksort($files);
 
-        return substr($commonPath, 0, -1);
+        if ($this->isNotRoot($commonPath)) {
+            $commonPath = substr($commonPath, 0, -1);
+        }
+        return $commonPath;
+    }
+
+    /**
+     * @param $commonPath
+     * @return bool
+     */
+    private function isNotRoot($commonPath)
+    {
+        return strlen($commonPath) > 1;
     }
 }

tests/PHP/CodeCoverage/Report/FactoryTest.php

@@ -231,6 +231,17 @@ public function reducePathsProvider()
               '/home/sb/Money/MoneyBag.php' => array()
             )
           ),
+          array(
+            array(
+              'driveA/Money.php' => array(),
+              'driveB/MoneyBag.php' => array()
+            ),
+            '/',
+            array(
+              '/driveA/Money.php' => array(),
+              '/driveB/MoneyBag.php' => array()
+            )
+          ),
           array(
             array(
               'Money.php' => array()