function testPngBasicFunctions()
{
$gdImage = new GDImage('png');
$this->assertEquals('png', $gdImage->getImageType());
$this->assertEquals('png', $gdImage->getImageExtension());
$this->assertEquals('image/png', $gdImage->getImageContentType());
$this->assertEquals('./images/code_bg.png', $gdImage->_getImageSrc('code_bg'));
$this->assertEquals(TRUE, $gdImage->isImageTypeValid('png'));
$this->assertEquals(FALSE, $gdImage->isImageTypeValid('xxx'));
print_r($gdImage->getErrors());
}