public function testConcat($concatArray = [], $expect = null)
{
/* setup */
$optionArray = ['directory' => Stream::url('root/cache/styles')];
$link = Head\Link::getInstance();
$link->init('concat');
foreach ($concatArray as $key => $value) {
$link->append($value);
}
$link->concat($optionArray)->concat($optionArray);
/* actual */
$actual = $link;
/* compare */
$this->assertEquals($this->normalizeEOL($expect), $actual);
}