Should you ever need a Request object to give to some particular function, you can ask RequestHelper service.
Simply call it via the shortcut $this->getRequest() in your spec files.
Method signature :
<?php
public function getRequest($method = null, $url = null, array $parameters = array());You can call it without arguments and it will return a blank new Request instance. You can then fill it with whatever you want.
Or you can call it with arguments. First two are the only mandatory ones in this case. Request Helper will call the router to fill your Request object with proper attributes.
$request->query or $request->request, depending on the method passed as a first argument./!\ The second parameter, $url, is used with a route, relative to your website root. Simply pass the path part of your routing.
Example :
<?php
[...] // Inside a spec function...
// Blank Request object
$request = $this->getRequest();
// Request object filled without parameters
$request = $this->getRequest('get', '/entity/tag/1');
// Request object with parameters, say for testing form
$request = $this->getRequest('post', '/save/entity', array('entity' => $entity));