Add polyfill for older PHPUnit (createMock)

Author: colinmollenhour

tests/CredisTestCommon.php

@@ -151,6 +151,18 @@ public static function tearDownAfterClass()
         }
     }
 
+    /**
+     * Polyfill for older PHPUnit
+     */
+    public function createMock($class)
+    {
+        if (method_exists($this, 'getMock')) {
+            return $this->getMock($class);
+        } else {
+            return parent::createMock($class);
+        }
+    }
+    
     /**
      * Polyfill for older PHPUnit
      */