public function testGetCreatedAt()
 {
     $git = new VersionControl_Git(dirname(__FILE__) . '/fixtures/001_VersionControl_Git');
     $instance = new VersionControl_Git_Object_Commit($git, '4ed54abb8efca38a0c794ca414b1f296279e0d85');
     $instance->setAuthor('author Kousuke Ebihara <*****@*****.**> 1264003801 +0900');
     $this->assertEquals(date('YmdHis', $instance->getCreatedAt()), '20100121011001');
     $instance->setAuthor('author Kousuke Ebihara <*****@*****.**>');
     $this->assertNull($instance->getCreatedAt());
 }