public function testOutputPng()
{
$image = $this->createImage(200, 100, 'png');
$resize = new ImageResize($image);
ob_start();
// supressing header errors
@$resize->output();
$image_contents = ob_get_clean();
$info = finfo_open();
$type = finfo_buffer($info, $image_contents, FILEINFO_MIME_TYPE);
$this->assertEquals('image/png', $type);
}