add unit test

Author: steven10a

examples/basic/agents_sdk.py

@@ -72,10 +72,6 @@ async def main() -> None:
                     run_config=RunConfig(tracing_disabled=True),
                     session=session,
                 )
-                agent = result.new_items[0].agent
-                print(f"Input guardrails: {[x.name for x in agent.input_guardrails]}")
-                breakpoint()
-                print(f"Output guardrails: {[x.name for x in agent.output_guardrails]}")
                 print(f"Assistant: {result.final_output}")
             except EOFError:
                 print("\nExiting.")

src/guardrails/agents.py

@@ -356,7 +356,10 @@ def _extract_text_from_input(input_data: Any) -> str:
         return input_data
 
     # If it's a list (conversation history), extract the latest user message
-    if isinstance(input_data, list) and len(input_data) > 0:
+    if isinstance(input_data, list):
+        if len(input_data) == 0:
+            return ""  # Empty list returns empty string
+
         # Iterate from the end to find the latest user message
         for msg in reversed(input_data):
             if isinstance(msg, dict):
@@ -381,6 +384,9 @@ def _extract_text_from_input(input_data: Any) -> str:
                     elif content is not None:
                         return str(content)
 
+        # No user message found in list
+        return ""
+
     # Fallback: convert to string
     return str(input_data)
 
@@ -483,7 +489,7 @@ async def single_guardrail(ctx: RunContextWrapper[None], agent: Agent, input_dat
 
         # Set the function name to the guardrail name (e.g., "Moderation" → "Moderation")
         single_guardrail.__name__ = guardrail.definition.name.replace(" ", "_")
-        
+
         return single_guardrail
 
     guardrail_functions = []