diff --git a/src/Symfony/Component/Mailer/Bridge/Sendgrid/Tests/Transport/SendgridSmtpTransportTest.php b/src/Symfony/Component/Mailer/Bridge/Sendgrid/Tests/Transport/SendgridSmtpTransportTest.php
new file mode 100644
index 0000000000000..77e5135c55cc4
--- /dev/null
+++ b/src/Symfony/Component/Mailer/Bridge/Sendgrid/Tests/Transport/SendgridSmtpTransportTest.php
@@ -0,0 +1,40 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Component\Mailer\Bridge\Sendgrid\Tests\Transport;
+
+use PHPUnit\Framework\TestCase;
+use Symfony\Component\Mailer\Bridge\Sendgrid\Transport\SendgridSmtpTransport;
+
+class SendgridSmtpTransportTest extends TestCase
+{
+    /**
+     * @dataProvider getTransportData
+     */
+    public function testToString(SendgridSmtpTransport $transport, string $expected)
+    {
+        $this->assertSame($expected, (string) $transport);
+    }
+
+    public static function getTransportData()
+    {
+        return [
+            [
+                new SendgridSmtpTransport('KEY'),
+                'smtps://smtp.sendgrid.net',
+            ],
+            [
+                new SendgridSmtpTransport('KEY', null, null, 'eu'),
+                'smtps://smtp.eu.sendgrid.net',
+            ],
+        ];
+    }
+}