diff --git a/tests/e2e/Services/Messaging/MessagingBase.php b/tests/e2e/Services/Messaging/MessagingBase.php
index 956ac5f68a..b3d760e6cc 100644
--- a/tests/e2e/Services/Messaging/MessagingBase.php
+++ b/tests/e2e/Services/Messaging/MessagingBase.php
@@ -444,6 +444,17 @@ trait MessagingBase
         $this->assertEquals($target['body']['userId'], $response['body']['target']['userId']);
         $this->assertEquals($target['body']['providerType'], $response['body']['target']['providerType']);
 
+        // Test duplicate subscribers not allowed
+        $response = $this->client->call(Client::METHOD_POST, '/messaging/topics/' . $topics['public']['$id'] . '/subscribers', \array_merge([
+            'content-type' => 'application/json',
+            'x-appwrite-project' => $this->getProject()['$id'],
+        ], $this->getHeaders()), [
+            'subscriberId' => ID::unique(),
+            'targetId' => $target['body']['$id'],
+        ]);
+
+        $this->assertEquals(409, $response['headers']['status-code']);
+
         $topic = $this->client->call(Client::METHOD_GET, '/messaging/topics/' . $topics['public']['$id'], [
             'content-type' => 'application/json',
             'x-appwrite-project' => $this->getProject()['$id'],