/**
* 测试[Arr::extract]的功能
*
* @dataProvider dataExtract
* @param mixed $arr
* @param mixed $paths
* @param mixed $expected
* @param mixed $default
*/
public function testExtract($arr, $paths, $expected, $default = null)
{
$this->assertEquals($expected, Arr::extract($arr, $paths, $default));
}