Testing Guzzle Clients

Testing Guzzle Clients

Guzzle provides several tools that will enable you to easily mock the HTTP layer without needing to send requests over the internet.

Mock handler
History middleware
Node.js web server for integration testing

Mock Handler

When testing HTTP clients, you often need to simulate specific scenarios like returning a successful response, returning an error, or returning specific responses in a certain order. Because unit tests need to be predictable, easy to bootstrap, and fast, hitting an actual remote API is a test smell.

Guzzle provides a mock handler that can be used to fulfill HTTP requests with a response or exception by shifting return values off of a queue.

use GuzzleHttp\Client;
use GuzzleHttp\Handler\MockHandler;
use GuzzleHttp\HandlerStack;
use GuzzleHttp\Psr7\Response;
use GuzzleHttp\Psr7\Request;
use GuzzleHttp\Exception\RequestException;
// Create a mock and queue two responses.
$mock = new MockHandler([
    new Response(200, ['X-Foo' => 'Bar']),
    new Response(202, ['Content-Length' => 0]),
    new RequestException("Error Communicating with Server", new Request('GET', 'test'))
]);
$handler = HandlerStack::create($mock);
$client = new Client(['handler' => $handler]);
// The first request is intercepted with the first response.
echo $client->request('GET', '/')->getStatusCode();
//> 200
// The second request is intercepted with the second response.
echo $client->request('GET', '/')->getStatusCode();
//> 202

When no more responses are in the queue and a request is sent, an OutOfBoundsException is thrown.

History Middleware

When using things like the Mock handler, you often need to know if the requests you expected to send were sent exactly as you intended. While the mock handler responds with mocked responses, the history middleware maintains a history of the requests that were sent by a client.

use GuzzleHttp\Client;
use GuzzleHttp\HandlerStack;
use GuzzleHttp\Middleware;
$container = [];
$history = Middleware::history($container);
$stack = HandlerStack::create();
// Add the history middleware to the handler stack.
$stack->push($history);
$client = new Client(['handler' => $stack]);
$client->request('GET', 'http://httpbin.org/get');
$client->request('HEAD', 'http://httpbin.org/get');
// Count the number of transactions
echo count($container);
//> 2
// Iterate over the requests and responses
foreach ($container as $transaction) {
    echo $transaction['request']->getMethod();
    //> GET, HEAD
    if ($transaction['response']) {
        echo $transaction['response']->getStatusCode();
        //> 200, 200
    } elseif ($transaction['error']) {
        echo $transaction['error'];
        //> exception
    }
    var_dump($transaction['options']);
    //> dumps the request options of the sent request.
}

Test Web Server

Using mock responses is almost always enough when testing a web service client. When implementing custom HTTP handlers, you’ll need to send actual HTTP requests in order to sufficiently test the handler. However, a best practice is to contact a local web server rather than a server over the internet.

Tests are more reliable
Tests do not require a network connection
Tests have no external dependencies

Using the test server

Warning

The following functionality is provided to help developers of Guzzle develop HTTP handlers. There is no promise of backwards compatibility when it comes to the node.js test server or the GuzzleHttp\Tests\Server class. If you are using the test server or Server class outside of guzzlehttp/guzzle, then you will need to configure autoloading and ensure the web server is started manually.

Hint

You almost never need to use this test web server. You should only ever consider using it when developing HTTP handlers. The test web server is not necessary for mocking requests. For that, please use the Mock handler and history middleware.

Guzzle ships with a node.js test server that receives requests and returns responses from a queue. The test server exposes a simple API that is used to enqueue responses and inspect the requests that it has received.

Any operation on the Server object will ensure that the server is running and wait until it is able to receive requests before returning.

GuzzleHttp\Tests\Server provides a static interface to the test server. You can queue an HTTP response or an array of responses by calling Server::enqueue(). This method accepts an array of Psr\Http\Message\ResponseInterface and Exception objects.

use GuzzleHttp\Client;
use GuzzleHttp\Psr7\Response;
use GuzzleHttp\Tests\Server;
// Start the server and queue a response
Server::enqueue([
    new Response(200, ['Content-Length' => 0])
]);
$client = new Client(['base_uri' => Server::$url]);
echo $client->request('GET', '/foo')->getStatusCode();
// 200

When a response is queued on the test server, the test server will remove any previously queued responses. As the server receives requests, queued responses are dequeued and returned to the request. When the queue is empty, the server will return a 500 response.

You can inspect the requests that the server has retrieved by calling Server::received().

foreach (Server::received() as $response) {
    echo $response->getStatusCode();
}

You can clear the list of received requests from the web server using the Server::flush() method.

Server::flush();
echo count(Server::received());
// 0