Updated TimestampBehaviorTest to test the callable in array format as value

tests/framework/behaviors/TimestampBehaviorTest.php

@@ -107,6 +107,7 @@ class TimestampBehaviorTest extends TestCase
             [new Expression("strftime('%Y')"), date('Y')],
             ['2015-10-20', '2015-10-20'],
             [time(), time()],
+            [[$this, 'arrayCallable'], '2015-10-20'],
         ];
     }
 
@@ -133,6 +134,11 @@ class TimestampBehaviorTest extends TestCase
         $this->assertEquals($expected, $model->updated_at);
     }
 
+    public function arrayCallable($event)
+    {
+        return '2015-10-20';
+    }
+
     /**
      * @depends testNewRecord
      */