diff --git a/src/effect/schema/tests.ts b/src/effect/schema/tests.ts
index 64a465e..8d1ce62 100644
--- a/src/effect/schema/tests.ts
+++ b/src/effect/schema/tests.ts
@@ -1 +1,10 @@
 import { Schema as S } from "@effect/schema"
+import { MutableClass } from "./MutableClass"
+
+
+class User extends MutableClass<User>("User")({
+    id: S.BigIntFromSelf
+}) {}
+
+const user = new User({ id: 1n })
+user.id = 2n