Add tests for full coverage of tool validation branches

- Add test cases for valid create_message calls that pass validation
  (covering branches 261->266, 266->272, 269->272 in session.py)
- Add test for CreateMessageResult.content_as_list with single content
  (covering line 1245 else branch in types.py)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

Author: ochafik

tests/server/test_session.py

@@ -360,6 +360,29 @@ async def test_create_message_tool_result_validation():
                     tools=[tool],
                 )
 
+            # Case 5: text-only message with tools (no tool_results) - passes validation
+            # This covers branch 261->266 (has_tool_results=False) and 266->272
+            # We use move_on_after since send_request will block waiting for response
+            with anyio.move_on_after(0.01):
+                await session.create_message(
+                    messages=[types.SamplingMessage(role="user", content=text)],
+                    max_tokens=100,
+                    tools=[tool],
+                )
+
+            # Case 6: valid matching tool_result/tool_use IDs - passes validation
+            # This covers branch 269->272 (IDs match, no error raised)
+            with anyio.move_on_after(0.01):
+                await session.create_message(
+                    messages=[
+                        types.SamplingMessage(role="user", content=text),
+                        types.SamplingMessage(role="assistant", content=tool_use),
+                        types.SamplingMessage(role="user", content=tool_result),
+                    ],
+                    max_tokens=100,
+                    tools=[tool],
+                )
+
 
 @pytest.mark.anyio
 async def test_other_requests_blocked_before_initialization():

tests/test_types.py

@@ -253,6 +253,11 @@ async def test_create_message_result_with_tool_use():
     assert result.stopReason == "toolUse"
     assert result.model == "claude-3"
 
+    # Test content_as_list with single content (covers else branch)
+    content_list = result.content_as_list
+    assert len(content_list) == 1
+    assert content_list[0] == result.content
+
 
 @pytest.mark.anyio
 async def test_client_capabilities_with_sampling_tools():