Adds tests for the GitHub tags

app/Shell/GitHubDockerTags.php

@@ -37,7 +37,9 @@ protected function getToken(): string
 
         $response = $this->guzzle->get('https://ghcr.io/token?' . http_build_query([
             'scope' => "repository:{$image}:pull",
-        ]));
+        ]), [
+            "http_errors" => false,
+        ]);
 
         if ($response->getStatusCode() !== 200) {
             throw new RuntimeException("Something went wrong getting the Token from GitHub's registry.");

tests/Feature/GitHubTagsTest.php

@@ -0,0 +1,59 @@
+<?php
+
+namespace Tests\Feature;
+
+use App\Services\Buggregator;
+use App\Shell\DockerTags;
+use App\Shell\GitHubDockerTags;
+use GuzzleHttp\Client;
+use GuzzleHttp\Handler\MockHandler;
+use GuzzleHttp\HandlerStack;
+use GuzzleHttp\Psr7\Response;
+use Mockery as M;
+use RuntimeException;
+use Tests\TestCase;
+
+class GitHubTagsTest extends TestCase
+{
+    /** @test */
+    function it_fetches_latest_tag()
+    {
+        $handlerStack = HandlerStack::create($this->mockImagesResponseHandler());
+        $client = new Client(['handler' => $handlerStack]);
+
+        /** @var DockerTags $dockerTags */
+        $dockerTags = M::mock(GitHubDockerTags::class, [$client, app(Buggregator::class)])->makePartial();
+
+        $this->assertEquals('latest', $dockerTags->getLatestTag());
+    }
+
+    /** @test */
+    function it_throws_exception_when_token_request_fails()
+    {
+        $handlerStack = HandlerStack::create($this->mockImagesResponseHandler(false));
+        $client = new Client(['handler' => $handlerStack]);
+
+        /** @var DockerTags $dockerTags */
+        $dockerTags = M::mock(GitHubDockerTags::class, [$client, app(Buggregator::class)])->makePartial();
+
+        $this->expectException(RuntimeException::class);
+
+        $dockerTags->getLatestTag();
+    }
+
+    private function mockImagesResponseHandler($tokenWorks = true)
+    {
+        return new MockHandler([
+            new Response($tokenWorks ? 200 : 400, [], json_encode([
+                'token' => 'fake-token',
+            ])),
+            new Response(200, [], json_encode([
+                'tags' => [
+                    'latest',
+                    '1.0.0',
+                    '1.0.0.rc-1',
+                ],
+            ])),
+        ]);
+    }
+}