Injecting single-use object into class - php

Question

I have the following code:
<?php
class X
{
public function do($url)
{
$httpRequest = new \HttpRequest\Curl($url, $this->getOptions());
$httpRequest->fire();
// etc.
}
// ...
}
In order to be able to unit test this class, I'd like to inject a mocked HttpRequest class. One way to do this would be as follows:
<?php
class X
{
private $httpRequestClass;
public function __construct($httpRequestClass = '\HttpRequest\Curl')
{
$this->httpRequestClass = $httpRequestClass;
}
public function do($url)
{
$httpRequest = new $this->httpRequestClass($url, $this->getOptions());
$httpRequest->fire();
// etc.
}
// ...
}
But this doesn't seem right. Any other ideas?

Answer 1

public function __construct($url, $httpRequestClass = null)
{
$this->url = $url;
if ($httpRequestClass == null) //> Default
$this->httpRequestClass = new HttpRequest\Curl($this->url);
else
$this->httpRequestClass = $httpRequestClass;
}
so when you are using this class normally just call it with one param
yourClass('your url');
Otherwise pass the istance in the second argument
yourClass('url', new MockedObj);
Of course you should always Inject your dependencies without providing a default object

Answer 2

The class needs to generate objects of type HttpRequest, but we don't necessarily want it to initialize an object: we may want it to use the prototype pattern, for example. Therefore, the class calls for the factory pattern. I chose a factory callback, as opposed to a factory class, for brevity.
<?php
class X
{
private $factoryCallback;
public function __construct($factoryCallback = null)
{
$this->factoryCallback = $factoryCallback;
}
public function do($url)
{
$httpRequest = $this->createHttpRequest($url);
$httpRequest->fire();
// etc.
}
private function createHttpRequest($url)
{
$callback = $this->factoryCallback;
if (is_callable($callback)) {
return $callback($url, $this->getOptions());
}
return new \HttpRequest\Curl($url, $this->getOptions());
}
// ...
}
The helper method, createHttpRequest(), is a bit redundant in this example, but would be used for error handling in production code.