Implement test_invalid_target_type to validate VuMark database type checking

The test verifies that InvalidTargetTypeError is raised when attempting to generate a VuMark instance using credentials from a CloudDatabase (non-VuMark) database. This was previously a stub pending the mock implementation in vws-python-mock#2961.

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

Author: adamtheturtle

tests/test_vws_exceptions.py

@@ -385,11 +385,34 @@ def test_invalid_instance_id(
     assert exc.value.response.status_code == HTTPStatus.UNPROCESSABLE_ENTITY
 
 
-def test_invalid_target_type() -> None:
+def test_invalid_target_type(
+    vws_client: VWS,
+    _mock_database: CloudDatabase,  # noqa: PT019
+    high_quality_image: io.BytesIO,
+) -> None:
     """
-    See https://github.com/VWS-Python/vws-python-mock/issues/2961 for
-    writing this test.
+    An ``InvalidTargetType`` exception is raised when trying to generate
+    a VuMark instance from a non-VuMark database.
     """
+    target_id = vws_client.add_target(
+        name="example_target",
+        width=1,
+        image=high_quality_image,
+        active_flag=True,
+        application_metadata=None,
+    )
+    vumark_service = VuMarkService(
+        server_access_key=_mock_database.server_access_key,
+        server_secret_key=_mock_database.server_secret_key,
+    )
+    with pytest.raises(expected_exception=InvalidTargetTypeError) as exc:
+        vumark_service.generate_vumark_instance(
+            target_id=target_id,
+            instance_id="example_instance_id",
+            accept=VuMarkAccept.PNG,
+        )
+
+    assert exc.value.response.status_code == HTTPStatus.UNPROCESSABLE_ENTITY
 
 
 def test_base_exception(