diff --git a/tests/unit/functions/test_remote_function_utils.py b/tests/unit/functions/test_remote_function_utils.py
index 0e4ca7a2ac..687c599985 100644
--- a/tests/unit/functions/test_remote_function_utils.py
+++ b/tests/unit/functions/test_remote_function_utils.py
@@ -217,13 +217,62 @@ def test_package_existed_helper():
     assert not _utils._package_existed([], "pandas")
 
 
+# Helper functions for signature inspection tests
+def _func_one_arg_annotated(x: int) -> int:
+    """A function with one annotated arg and an annotated return type."""
+    return x
+
+
+def _func_one_arg_unannotated(x):
+    """A function with one unannotated arg and no return type annotation."""
+    return x
+
+
+def _func_two_args_annotated(x: int, y: str):
+    """A function with two annotated args and no return type annotation."""
+    return f"{x}{y}"
+
+
+def _func_two_args_unannotated(x, y):
+    """A function with two unannotated args and no return type annotation."""
+    return f"{x}{y}"
+
+
+def test_has_conflict_input_type_too_few_inputs():
+    """Tests conflict when there are fewer input types than parameters."""
+    signature = inspect.signature(_func_one_arg_annotated)
+    assert _utils.has_conflict_input_type(signature, input_types=[])
+
+
+def test_has_conflict_input_type_too_many_inputs():
+    """Tests conflict when there are more input types than parameters."""
+    signature = inspect.signature(_func_one_arg_annotated)
+    assert _utils.has_conflict_input_type(signature, input_types=[int, str])
+
+
+def test_has_conflict_input_type_type_mismatch():
+    """Tests has_conflict_input_type with a conflicting type annotation."""
+    signature = inspect.signature(_func_two_args_annotated)
+
+    # The second type (bool) conflicts with the annotation (str).
+    assert _utils.has_conflict_input_type(signature, input_types=[int, bool])
+
+
+def test_has_conflict_input_type_no_conflict_annotated():
+    """Tests that a matching, annotated signature is compatible."""
+    signature = inspect.signature(_func_two_args_annotated)
+    assert not _utils.has_conflict_input_type(signature, input_types=[int, str])
+
+
+def test_has_conflict_input_type_no_conflict_unannotated():
+    """Tests that a signature with no annotations is always compatible."""
+    signature = inspect.signature(_func_two_args_unannotated)
+    assert not _utils.has_conflict_input_type(signature, input_types=[int, float])
+
+
 def test_has_conflict_output_type_no_conflict():
     """Tests has_conflict_output_type with type annotation."""
-    # Helper functions with type annotation for has_conflict_output_type.
-    def _func_with_return_type(x: int) -> int:
-        return x
-
-    signature = inspect.signature(_func_with_return_type)
+    signature = inspect.signature(_func_one_arg_annotated)
 
     assert _utils.has_conflict_output_type(signature, output_type=float)
     assert not _utils.has_conflict_output_type(signature, output_type=int)
@@ -231,11 +280,7 @@ def _func_with_return_type(x: int) -> int:
 
 def test_has_conflict_output_type_no_annotation():
     """Tests has_conflict_output_type without type annotation."""
-    # Helper functions without type annotation for has_conflict_output_type.
-    def _func_without_return_type(x):
-        return x
-
-    signature = inspect.signature(_func_without_return_type)
+    signature = inspect.signature(_func_one_arg_unannotated)
 
     assert not _utils.has_conflict_output_type(signature, output_type=int)
     assert not _utils.has_conflict_output_type(signature, output_type=float)