diff --git a/SVSim.UnitTests/Controllers/UserMyPageControllerTests.cs b/SVSim.UnitTests/Controllers/UserMyPageControllerTests.cs
index 92a19bb..262ab9f 100644
--- a/SVSim.UnitTests/Controllers/UserMyPageControllerTests.cs
+++ b/SVSim.UnitTests/Controllers/UserMyPageControllerTests.cs
@@ -212,4 +212,17 @@ public class UserMyPageControllerTests
         Assert.That(list[0].GetString(), Is.EqualTo("1211410310"));
         Assert.That(list[7].GetString(), Is.EqualTo("1218410310"));
     }
+
+    [Test]
+    public async Task Update_without_auth_returns_401()
+    {
+        using var factory = new SVSimTestFactory();
+        var client = factory.CreateClient();  // NO X-Test-Viewer-Id header
+
+        var body = JsonBody("""
+            {"select_type":0,"mypage_id":"0","mypage_id_list":[]}
+            """);
+        var response = await client.PostAsync("/user_mypage/update", body);
+        Assert.That(response.StatusCode, Is.EqualTo(System.Net.HttpStatusCode.Unauthorized));
+    }
 }