How to provide a mock entity manager to test a service class? - php

Question

I have a service class (OutletScraper) in my Symfony (3.4) application. The class uses Entity Manager and a Geocoding service provided by the Bazinga Geocoder bundle. I've configured both successfully so that I am able to call them from within my service class. Whenever I need the service, I am calling it from the container so the entity manager and geocoder bundle is injected into it already.
When testing, I understand that I can mock the entity manager and then provide this to my test class. As I am accessing the service class from the container, how do I override what gets passed to the constructor? ie so that I can provide the mock entity manager instead of it being injected with the real one. I tried to instantiate an object of the service class manually:
$outletScraper = new OutletScraper(new Provider(), $this->createMock(EntityManagerInterface::class));
However I get the following error when doing so:
Error: Cannot instantiate interface Geocoder\Provider\Provider
How can I instantiate this class correctly? Do I need to call it from the service container (its set to private)? Appreciate any help.

Answer 1

Your mock of the entity manager works fine, the problem is the geocoder provider. Just like EntityManagerInterface, Geocoder\Provider\Provider is also an interface. The library maintainers just chose to omit the suffix.
That means you can't just create it, but instead have to pass a concrete class implementing the interface, like Geocoder\Provider\GoogleMaps\GoogleMaps, if you actually want to do the geocoding call or mock the Provider as well.
If you want to check if your configured geocoding provider works you can write a functional test using Symfony's WebTestCase, that looks roughly something like this:
<?php
namespace AppBundle\Tests\Scraper;
use Symfony\Bundle\FrameworkBundle\Test\WebTestCase;
class OutletScraperTest extends WebTestCase
{
public function testFindsLocation()
{
// This will instantiate your Symfony application in the test environment
$client = static::createClient();
$container = $client->getContainer();
// Replace the class name with the service id, if you use artificial service ids like "app.outlet_scraper"
$scraper = $container->get(OutletScraper::class);
// Call whatever method you want to test on your outlet scraper
$result = $scraper->someMethod();
// Assert result matches expectations
$this->assertEquals(..., $result);
}
}
Be careful though, that this will use the OutletScraper you configured for your application, with both actual dependencies. So your geocode provider will make an actual call to whatever provider you use, which might use up requests, which might be limited. Also you will use the real Doctrine EntityManager, meaning whatever you write to the database will actually be written. Especially for the database you should therefore create a separate test database and configure it in your app/config/config_test.yaml.

Answer 2

My recommendation would be that if you are trying to test this service alone, you should also mock the Geocoder\Provider\Provider. Otherwise, your test assertions could bring up different results depending on when you run them.
If you are going to use this mock a lot, you could even create your own testing class that implements that interface, so that you can prepare the different outputs yourself on your test environment.