public function testIsFlush()
 {
     $controller = new Controller();
     $req = new SS_HTTPRequest('GET', '/', array('flush' => 1));
     $controller->setRequest($req);
     $this->assertTrue(Cacheable::is_flush($controller));
     $req = new SS_HTTPRequest('GET', '/', array('flush' => 'all'));
     $controller->setRequest($req);
     $this->assertTrue(Cacheable::is_flush($controller));
     $req = new SS_HTTPRequest('GET', '/', array('fluff' => 1));
     $controller->setRequest($req);
     $this->assertFalse(Cacheable::is_flush($controller));
 }