app/Listeners/VerifyDatabaseIsReachable.php

@@ -0,0 +1,23 @@
+<?php
+
+namespace App\Listeners;
+
+use Illuminate\Foundation\Events\DiagnosingHealth;
+use Illuminate\Support\Facades\DB;
+use RuntimeException;
+use Throwable;
+
+class VerifyDatabaseIsReachable
+{
+    /**
+     * A container whose database is unreachable is not healthy, however well it serves /up.
+     */
+    public function handle(DiagnosingHealth $event): void
+    {
+        try {
+            DB::connection()->select('select 1');
+        } catch (Throwable $e) {
+            throw new RuntimeException('The database is not reachable: '.$e->getMessage(), previous: $e);
+        }
+    }
+}

tests/Feature/EventListenerRegistrationTest.php

@@ -9,6 +9,7 @@
 use App\Events\RouteActivated;
 use App\Events\RouteArticleApproved;
 use Illuminate\Contracts\Debug\ExceptionHandler;
+use Illuminate\Foundation\Events\DiagnosingHealth;
 use Illuminate\Support\Facades\Event;
 use PHPUnit\Framework\Attributes\DataProvider;
 use RuntimeException;
@@ -28,6 +29,7 @@ public static function eventProvider(): array
             'NewArticleFetched' => [NewArticleFetched::class],
             'RouteActivated' => [RouteActivated::class],
             'RouteArticleApproved' => [RouteArticleApproved::class],
+            'DiagnosingHealth' => [DiagnosingHealth::class],
         ];
     }
 

tests/Feature/HealthEndpointTest.php

@@ -0,0 +1,41 @@
+<?php
+
+namespace Tests\Feature;
+
+use App\Listeners\VerifyDatabaseIsReachable;
+use Illuminate\Foundation\Events\DiagnosingHealth;
+use Illuminate\Support\Facades\DB;
+use RuntimeException;
+use Tests\TestCase;
+
+class HealthEndpointTest extends TestCase
+{
+    public function test_up_returns_ok_when_the_database_is_reachable(): void
+    {
+        $this->get('/up')->assertOk();
+    }
+
+    public function test_up_fails_when_the_database_is_unreachable(): void
+    {
+        DB::shouldReceive('connection')->andThrow(new RuntimeException('getaddrinfo for db failed'));
+
+        $this->get('/up')->assertServerError();
+    }
+
+    public function test_the_listener_throws_when_the_connection_fails(): void
+    {
+        DB::shouldReceive('connection')->andThrow(new RuntimeException('getaddrinfo for db failed'));
+
+        $this->expectException(RuntimeException::class);
+        $this->expectExceptionMessage('The database is not reachable');
+
+        app(VerifyDatabaseIsReachable::class)->handle(new DiagnosingHealth);
+    }
+
+    public function test_the_listener_passes_when_the_connection_works(): void
+    {
+        app(VerifyDatabaseIsReachable::class)->handle(new DiagnosingHealth);
+
+        $this->addToAssertionCount(1);
+    }
+}