public function testStringExtraction()
{
$result = String::extract('/string/', 'whole string');
$this->assertEqual('string', $result);
$this->assertFalse(String::extract('/not/', 'whole string'));
$this->assertEqual('part', String::extract('/\\w+\\s*(\\w+)/', 'second part', 1));
$this->assertNull(String::extract('/\\w+\\s*(\\w+)/', 'second part', 2));
}