How to unit test if function has been called? Dependency injection? - unit-testing

Question

I'm creating a simple RESTful API in PHP for practice. I'm trying to write as testable code as possible. After reading many tutorials and watching a few videos, I still feel at a loss on how to design this.
Basically, I have set up a Router class. It is responsible for mapping url paths to controller methods.
It's easy to test the router's state after adding a route.
But, how do I test if the proper class->function(params) has been called in respond()?
I'm using PHPUnit, and I've been reading about mocks. I don't know how to use them in this context.
Currently, respond() parses a given path and request method, and calls the mapped method.
Here is my current design:
private $routes;
public function __construct() {
$routes = array();
}
/**
* Gets all current routes
*/
public function getRoutes();
/**
* Sets all routes
*/
public function setRoutes($routes);
/**
* Routes GET request
*/
public function get();
/**
* Routes POST request
*/
public function post();
/**
* Routes PUT request
*/
public function put();
/**
* Routes DELETE request
*/
public function delete();
/**
* Sets up default paths for a given resource
*/
public function resource();
/**
* Respond to request
* #return mixed JSON of resource data
*/
public function respond($req_method, $request);
/**
* Returns mapped call info from request method and path
* #return mixed An array of the call and params
*/
private function parse($req_method, $request);

Answer 1

As the comments have indicated, this would be a good use of a spy or mocking system. PHPunit has some ability to create and test for mocks, but I prefer to use a different library - Mockery.
This code will create a class and test that that when you call average(), it's called three times, and then also returns a given value.
Your code would call respond(), after setting up a mock that shouldReceive('get')->once() (for example). The m::close in the teardown will verify that get() was called, just one time, and would fail the test if it was not.
<?php
use \Mockery as m;
class TemperatureTest extends PHPUnit_Framework_TestCase
{
public function tearDown()
{
m::close();
}
public function testGetsAverageTemperatureFromThreeServiceReadings()
{
$service = m::mock('service');
$service->shouldReceive('readTemp')->times(3)->andReturn(10, 12, 14);
$temperature = new Temperature($service);
$this->assertEquals(12, $temperature->average());
}
}
Since you would be calling a real class to do work in respond(), you will need a 'partial mock'
$restful= m::mock('RestfulController[get]');
$restful->shouldReceive('get')->once();