diff --git a/tests/test_function_schema.py b/tests/test_function_schema.py
index 54e7e2f9e..38d6d5e67 100644
--- a/tests/test_function_schema.py
+++ b/tests/test_function_schema.py
@@ -451,3 +451,37 @@ def foo(x: int) -> int:
 
     assert fs.name == "custom"
     assert fs.params_json_schema.get("title") == "custom_args"
+
+
+def test_unannotated_function_with_enforcement():
+    """Test enforcement raises error for unannotated parameters"""
+    def my_func(x): ...
+
+    with pytest.raises(ValueError) as exc_info:
+        function_schema(my_func, enforce_type_annotations=True)
+
+    assert "Parameter 'x' must be type-annotated" in str(exc_info.value)
+
+
+def test_unannotated_function_without_enforcement():
+    """Test fallback to Any when enforcement is off"""
+    def my_func(x): ...
+
+    schema = function_schema(my_func, enforce_type_annotations=False)
+    assert schema.params_json_schema["properties"]["x"]["type"] == "any"
+
+
+def test_annotated_function_works_with_enforcement():
+    """Test basic type hints work with enforcement"""
+    def my_func(x: int): ...
+
+    schema = function_schema(my_func, enforce_type_annotations=True)
+    assert schema.params_json_schema["properties"]["x"]["type"] == "integer"
+
+
+def test_positional_args_backward_compatibility():
+    """Ensure old positional args still work"""
+    def my_func(x: int): ...
+
+    schema = function_schema(my_func, "sphinx", enforce_type_annotations=False)
+    assert schema.name == "my_func"