[typespec-python] Add test cases for orphan model serialization (#3123)

* Initial plan

* Add test cases: uncomment orphan model serializable tests

Co-authored-by: msyyc <70930885+msyyc@users.noreply.github.com>

* Add changelog entry for orphan model serialization test cases

Co-authored-by: msyyc <70930885+msyyc@users.noreply.github.com>

* Change changeKind from feature to internal in changelog

Co-authored-by: msyyc <70930885+msyyc@users.noreply.github.com>

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: msyyc <70930885+msyyc@users.noreply.github.com>

Author: Copilot

.chronus/changes/copilot-fix-3122-2025-6-4-2-11-57.md

@@ -0,0 +1,7 @@
+---
+changeKind: internal
+packages:
+  - "@azure-tools/typespec-python"
+---
+
+Add test cases for orphan model serialization

packages/typespec-python/test/azure/mock_api_tests/asynctests/test_azure_client_generator_core_usage_async.py

@@ -31,8 +31,8 @@ async def test_model_usage(client: UsageClient):
     ) == await client.model_in_operation.model_in_read_only_property(body=models.RoundTripModel())
 
 
-# @pytest.mark.asyncio
-# async def test_orphan_model_serializable(client: UsageClient):
-#     await client.model_in_operation.orphan_model_serializable(
-#         body=models.OrphanModel(model_name="name", description="desc")
-#     )
+@pytest.mark.asyncio
+async def test_orphan_model_serializable(client: UsageClient):
+    await client.model_in_operation.orphan_model_serializable(
+        body=models.OrphanModel(model_name="name", description="desc")
+    )

packages/typespec-python/test/azure/mock_api_tests/test_azure_client_generator_core_usage.py

@@ -28,5 +28,5 @@ def test_model_usage(client: UsageClient):
     ) == client.model_in_operation.model_in_read_only_property(body=models.RoundTripModel())
 
 
-# def test_orphan_model_serializable(client: UsageClient):
-#     client.model_in_operation.orphan_model_serializable(body=models.OrphanModel(model_name="name", description="desc"))
+def test_orphan_model_serializable(client: UsageClient):
+    client.model_in_operation.orphan_model_serializable(body=models.OrphanModel(model_name="name", description="desc"))