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15.

Mocking Symfony's Http Client

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Having the ability to mock objects in tests is super awesome, and kind of weird and complex all at the same time. If we have simple objects, like Dinosaur, we should avoid the extra lines of code and just instantiate a real Dinosaur for the test. After all, it's pretty easy to control the behavior of Dinosaur just by calling its real methods. No need for the mock weirdness.

But, for more complex objects, like HttpClient, using the real client... can be a headache. The general rule of thumb is to use mocks for complex objects like, services... but for simple objects, like models or entities, just use the real thing.

Looking back at Symfony's HTTP Client, we were able to mock both the client and the response to control its behavior. But, because needing to do this sort of thing is so common, Symfony's HTTP Client comes with some special classes that can do the mocking for us. It comes with two real classes specifically made for testing: MockHttpClient & MockResponse. Using PHPUnit's mock system is fine, but these exist to make our life even easier.

Check it out: instead of creating a mock for $mockResponse, instantiate a MockResponse() passing in json_encode() with an array to mimic GitHub's API response. Grab Maverick's issue below and paste that into the array. Since MockResponse is already configured, remove the $mockResponse bits below.

82 lines | tests/Unit/Service/GithubServiceTest.php
// ... lines 1 - 8
use Symfony\Component\HttpClient\MockHttpClient;
use Symfony\Component\HttpClient\Response\MockResponse;
// ... lines 11 - 13
class GithubServiceTest extends TestCase
{
// ... lines 16 - 63
public function testExceptionThrownWithUnknownLabel(): void
{
$mockResponse = new MockResponse(json_encode([
[
'title' => 'Maverick',
'labels' => [['name' => 'Status: Drowsy']],
],
]));
// ... lines 72 - 79
}
}

For the client, remove $mockHttpClient and below, instantiate a new MockHttpClient() passing in $mockResponse instead. Since we're not doing anything with $mockLogger, cut createMock(), remove the variable, and paste that as an argument to GithubService().

82 lines | tests/Unit/Service/GithubServiceTest.php
// ... lines 1 - 8
use Symfony\Component\HttpClient\MockHttpClient;
use Symfony\Component\HttpClient\Response\MockResponse;
// ... lines 11 - 13
class GithubServiceTest extends TestCase
{
// ... lines 16 - 63
public function testExceptionThrownWithUnknownLabel(): void
{
$mockResponse = new MockResponse(json_encode([
[
'title' => 'Maverick',
'labels' => [['name' => 'Status: Drowsy']],
],
]));
$mockHttpClient = new MockHttpClient($mockResponse);
$service = new GithubService($mockHttpClient, $this->createMock(LoggerInterface::class));
// ... lines 75 - 79
}
}

Wow, this is looking better already! But, let's see what happens when we run the tests:

./vendor/bin/phpunit

And... Woah! All of the tests are passing!

But, the assertion count did go down to "16" because MockHttpClient and MockResponse do not actually perform any assertions, like how many times a method is called.

So... what's the actual benefit to using these mock classes? Why not just create our own via PHPUnit? Ha... Check out this diff of GithubService. We removed 11 lines of code by using the "built-in" mocks in just one test. Imagine how many lines of code we could remove by using them in all of our tests. Hm... I think that's exactly what we'll do next.