diff --git a/lib/Webhook/WebhookUserNotFound.php b/lib/Webhook/WebhookUserNotFound.php
new file mode 100644
index 0000000..9972062
--- /dev/null
+++ b/lib/Webhook/WebhookUserNotFound.php
@@ -0,0 +1,20 @@
+<?php
+
+declare(strict_types=1);
+
+namespace UserHub\Webhook;
+
+use UserHub\Code;
+use UserHub\UserHubError;
+
+/**
+ * WebhookUserNotFound is an error which can be used to indicate a user was
+ * not found in the onGetUser, onUpdateUser, and onDeleteUser methods.
+ */
+class WebhookUserNotFound extends UserHubError
+{
+    public function __construct()
+    {
+        parent::__construct(message: 'User not found', apiCode: Code::NotFound);
+    }
+}
diff --git a/tests/WebhookTest.php b/tests/WebhookTest.php
index b8de6dc..ba4bec8 100644
--- a/tests/WebhookTest.php
+++ b/tests/WebhookTest.php
@@ -6,12 +6,17 @@
 
 use PHPUnit\Framework\TestCase;
 use UserHub\Code;
+use UserHub\ConnectionsV1\CustomUser;
+use UserHub\ConnectionsV1\GetCustomUserRequest;
+use UserHub\ConnectionsV1\ListCustomUsersRequest;
+use UserHub\ConnectionsV1\ListCustomUsersResponse;
 use UserHub\EventsV1\Event;
 use UserHub\Internal\Constants;
 use UserHub\UserHubError;
 use UserHub\Webhook;
 use UserHub\Webhook\WebhookRequest;
 use UserHub\Webhook\WebhookResponse;
+use UserHub\Webhook\WebhookUserNotFound;
 
 /**
  * @internal
@@ -35,10 +40,27 @@ public function testHandle(
         $onError = static function (Exception $ex): void {};
 
         $webhook = new Webhook($secret, onError: $onError);
-        $webhook->onEvent(static function (Event $event): void {
-            if ('ok' !== $event->type) {
-                throw new UserHubError("Event failed: {$event->type}", apiCode: Code::InvalidArgument);
+
+        $webhook->onEvent(static function (Event $input): void {
+            if ('ok' !== $input->type) {
+                throw new UserHubError("Event failed: {$input->type}", apiCode: Code::InvalidArgument);
+            }
+        });
+
+        $webhook->onListUsers(static function (ListCustomUsersRequest $input): ListCustomUsersResponse {
+            if (100 !== $input->pageSize) {
+                throw new Error("unexpected page size {$input->pageSize}");
+            }
+
+            return new ListCustomUsersResponse(users: [], nextPageToken: '');
+        });
+
+        $webhook->onGetUser(static function (GetCustomUserRequest $input): CustomUser {
+            if ('not-found' === $input->id) {
+                throw new WebhookUserNotFound();
             }
+
+            return new CustomUser(id: $input->id);
         });
 
         if ($setTimestamp) {
@@ -383,6 +405,57 @@ public static function provideHandleCases(): iterable
                 false,
                 true,
             ],
+            [
+                'List users',
+                'test',
+                new WebhookRequest(
+                    headers: [
+                        'UserHub-Action' => 'users.list',
+                    ],
+                    body: '{"pageSize":100}',
+                ),
+                new WebhookResponse(
+                    statusCode: 200,
+                    body: '{"nextPageToken":"","users":[]}',
+                ),
+                true,
+                false,
+                true,
+            ],
+            [
+                'Get user',
+                'test',
+                new WebhookRequest(
+                    headers: [
+                        'UserHub-Action' => 'users.get',
+                    ],
+                    body: '{"id": "1"}',
+                ),
+                new WebhookResponse(
+                    statusCode: 200,
+                    body: '{"id":"1","displayName":"","email":"","emailVerified":false,"phoneNumber":"","phoneNumberVerified":false,"imageUrl":"","disabled":false}',
+                ),
+                true,
+                false,
+                true,
+            ],
+            [
+                'Get user not found',
+                'test',
+                new WebhookRequest(
+                    headers: [
+                        'UserHub-Action' => 'users.get',
+                    ],
+                    body: '{"id": "not-found"}',
+                ),
+                new WebhookResponse(
+                    statusCode: 404,
+                    body: '{"message":"User not found","code":"NOT_FOUND"}',
+                ),
+                true,
+                false,
+                true,
+            ],
         ];
     }
 }