The mock plugin is useful for testing Guzzle clients. The mock plugin allows you to queue an array of responses that will satisfy requests sent from a client by consuming the request queue in FIFO order.
use Guzzle\Http\Client;
use Guzzle\Plugin\Mock\MockPlugin;
use Guzzle\Http\Message\Response;
$client = new Client('http://www.test.com/');
$mock = new MockPlugin();
$mock->addResponse(new Response(200))
->addResponse(new Response(404));
// Add the mock plugin to the client object
$client->addSubscriber($mock);
// The following request will receive a 200 response from the plugin
$client->get('http://www.example.com/')->send();
// The following request will receive a 404 response from the plugin
$client->get('http://www.test.com/')->send();