feat: Add documentation to test file uploads (#1362)

Author: artandor

core/file-upload.md

@@ -297,3 +297,48 @@ uploaded cover, you can have a nice illustrated book record!
 
 Voilà! You can now send files to your API, and link them to any other resource
 in your app.
+
+## Testing
+
+To test your upload with `ApiTestCase`, you can write a method as below:
+
+```php
+<?php
+// tests/MediaObjectTest.php
+
+namespace App\Tests;
+
+use ApiPlatform\Core\Bridge\Symfony\Bundle\Test\ApiTestCase;
+use App\Entity\MediaObject;
+use Hautelook\AliceBundle\PhpUnit\RefreshDatabaseTrait;
+use Symfony\Component\HttpFoundation\File\UploadedFile;
+
+class MediaObjectTest extends ApiTestCase
+{
+    use RefreshDatabaseTrait;
+
+    public function testCreateAMediaObject(): void
+    {
+        $file = new UploadedFile('fixtures/files/image.png', 'image.png');
+        $client = self::createClient();
+
+        $client->request('POST', '/media_objects', [
+            'headers' => ['Content-Type' => 'multipart/form-data'],
+            'extra' => [
+                // If you have additional fields in your MediaObject entity, use the parameters.
+                'parameters' => [
+                    'title' => 'My file uploaded',
+                ],
+                'files' => [
+                    'file' => $file,
+                ],
+            ]
+        ]);
+        $this->assertResponseIsSuccessful();
+        $this->assertMatchesResourceItemJsonSchema(MediaObject::class);
+        $this->assertJsonContains([
+            'title' => 'My file uploaded',
+        ]);
+    }
+}
+```