Fix high-severity test quality issues (#3854)

- Delete entirely commented-out test_run_server.py (99 lines dead code)
- Fix test_pydantic_model_with_stringified_json_no_strict: replace
  try/except-both-branches-pass with clear pytest.raises assertion
- Fix test_path_traversal_blocked: remove dead assertions after
  pytest.raises (lines after raise never execute)

Error handling middleware test fixes are in a separate PR (#3858)
which also fixes the underlying RetryMiddleware bug.

🤖 Generated with Claude Code

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

tests/server/providers/test_skills_provider.py

@@ -653,14 +653,8 @@ class TestPathTraversalPrevention:
         mcp.add_provider(SkillsDirectoryProvider(roots=skills_dir))
 
         async with Client(mcp) as client:
-            # Path traversal attempts should fail (either normalized away or blocked)
-            # The important thing is that SECRET DATA is never returned
+            # Path traversal attempts should fail — the secret must never be returned
             with pytest.raises(Exception):
-                result = await client.read_resource(
+                await client.read_resource(
                     AnyUrl("skill://test-skill/../../../secret.txt")
                 )
-                # If we somehow got here, ensure we didn't get the secret
-                if result:
-                    for content in result:
-                        if hasattr(content, "text"):
-                            assert "SECRET DATA" not in content.text

tests/server/test_input_validation.py

@@ -13,6 +13,7 @@ from mcp.types import TextContent
 from pydantic import BaseModel
 
 from fastmcp import Client, FastMCP
+from fastmcp.exceptions import ToolError
 
 
 class UserProfile(BaseModel):
@@ -130,8 +131,13 @@ class TestPydanticModelArguments:
             assert "Alice" in result.content[0].text
             assert "30" in result.content[0].text
 
-    async def test_pydantic_model_with_stringified_json_no_strict(self):
-        """Test if stringified JSON is accepted for Pydantic models without strict validation."""
+    async def test_stringified_json_not_auto_parsed_for_pydantic_models(self):
+        """Stringified JSON is rejected for Pydantic model parameters.
+
+        Some LLM clients send stringified JSON (a JSON string containing a
+        JSON object) instead of a proper JSON object.  FastMCP does not
+        auto-parse these; callers get a validation error.
+        """
         mcp = FastMCP("TestServer", strict_input_validation=False)
 
         @mcp.tool
@@ -140,33 +146,12 @@ class TestPydanticModelArguments:
             return f"Created user {profile.name}, age {profile.age}"
 
         async with Client(mcp) as client:
-            # Some LLM clients send stringified JSON instead of actual JSON
             stringified = json.dumps(
                 {"name": "Bob", "age": 25, "email": "bob@example.com"}
             )
 
-            # This test verifies whether we handle stringified JSON
-            error_msg = ""
-            try:
-                result = await client.call_tool("create_user", {"profile": stringified})
-                # If this succeeds, we're handling stringified JSON
-                assert isinstance(result.content[0], TextContent)
-                assert "Bob" in result.content[0].text
-                stringified_json_works = True
-            except Exception as e:
-                # If this fails, we're not handling stringified JSON
-                stringified_json_works = False
-                error_msg = str(e)
-
-            # Document the behavior - we want to know if this works or not
-            if stringified_json_works:
-                # This is the desired behavior
-                pass
-            else:
-                # This means stringified JSON doesn't work - document it
-                assert (
-                    "validation" in error_msg.lower() or "invalid" in error_msg.lower()
-                )
+            with pytest.raises(ToolError, match="validation"):
+                await client.call_tool("create_user", {"profile": stringified})
 
     async def test_pydantic_model_with_coercion(self):
         """Pydantic models should benefit from coercion without strict validation."""

tests/server/test_run_server.py

@@ -1,98 +0,0 @@
-# from pathlib import Path
-# from typing import TYPE_CHECKING, Any
-
-# import pytest
-
-# import fastmcp
-# from fastmcp import FastMCP
-
-# if TYPE_CHECKING:
-#     pass
-
-# USERS = [
-#     {"id": "1", "name": "Alice", "active": True},
-#     {"id": "2", "name": "Bob", "active": True},
-#     {"id": "3", "name": "Charlie", "active": False},
-# ]
-
-
-# @pytest.fixture
-# def fastmcp_server():
-#     server = FastMCP("TestServer")
-
-#     # --- Tools ---
-
-#     @server.tool
-#     def greet(name: str) -> str:
-#         """Greet someone by name."""
-#         return f"Hello, {name}!"
-
-#     @server.tool
-#     def add(a: int, b: int) -> int:
-#         """Add two numbers together."""
-#         return a + b
-
-#     @server.tool
-#     def error_tool():
-#         """This tool always raises an error."""
-#         raise ValueError("This is a test error")
-
-#     # --- Resources ---
-
-#     @server.resource(uri="resource://wave")
-#     def wave() -> str:
-#         return "👋"
-
-#     @server.resource(uri="data://users")
-#     async def get_users() -> list[dict[str, Any]]:
-#         return USERS
-
-#     @server.resource(uri="data://user/{user_id}")
-#     async def get_user(user_id: str) -> dict[str, Any] | None:
-#         return next((user for user in USERS if user["id"] == user_id), None)
-
-#     # --- Prompts ---
-
-#     @server.prompt
-#     def welcome(name: str) -> str:
-#         return f"Welcome to FastMCP, {name}!"
-
-#     return server
-
-
-# @pytest.fixture
-# async def stdio_client():
-#     # Find the stdio.py script path
-#     base_dir = Path(__file__).parent
-#     stdio_script = base_dir / "test_servers" / "stdio.py"
-
-#     if not stdio_script.exists():
-#         raise FileNotFoundError(f"Could not find stdio.py script at {stdio_script}")
-
-#     client = fastmcp.Client(
-#         transport=fastmcp.client.transports.StdioTransport(
-#             command="python",
-#             args=[str(stdio_script)],
-#         )
-#     )
-
-#     async with client:
-#         print("READY")
-#         yield client
-#         print("DONE")
-
-
-# class TestRunServerStdio:
-#     async def test_run_server_stdio(
-#         self, fastmcp_server: FastMCP, stdio_client: fastmcp.Client
-#     ):
-#         print("TEST")
-#         tools = await stdio_client.list_tools()
-#         print("TEST 2")
-#         assert tools == 1
-
-
-# class TestRunServerSSE:
-#
-#     async def test_run_server_sse(self, fastmcp_server: FastMCP):
-#         pass