fix: Use mock stdin/stdout in tests

Author: Developer

tests/test_stdio_eof.py

@@ -1,42 +1,26 @@
 """Test that stdio server exits when stdin reaches EOF."""
-import asyncio
-import sys
-from io import StringIO
-
 import anyio
 import pytest
+from io import TextIOWrapper, BytesIO
 
 from mcp.server.stdio import stdio_server
 
 
 @pytest.mark.anyio
 async def test_stdio_server_exits_on_eof():
     """Server should exit gracefully when stdin is closed (EOF)."""
-    # Create a closed stdin (simulating parent death)
-    closed_stdin = StringIO()  # Empty, immediate EOF
-    
+    # Create a stdin that immediately returns EOF
+    empty_stdin = anyio.wrap_file(TextIOWrapper(BytesIO(b""), encoding="utf-8"))
+    empty_stdout = anyio.wrap_file(TextIOWrapper(BytesIO(), encoding="utf-8"))
+
     # This should complete without hanging
-    with anyio.move_on_after(5):  # 5 second timeout
-        async with stdio_server() as (read_stream, write_stream):
-            # Try to read from stream - should get EOF quickly
+    with anyio.move_on_after(5):
+        async with stdio_server(stdin=empty_stdin, stdout=empty_stdout) as (
+            read_stream,
+            write_stream,
+        ):
+            # Try to read from stream - should get EndOfStream quickly
             try:
                 await read_stream.receive()
             except anyio.EndOfStream:
-                pass  # Expected - stream closed
-    
-    # If we get here without timeout, test passes
-
-
-@pytest.mark.anyio  
-async def test_stdio_server_parent_death_simulation():
-    """Simulate parent process death by closing stdin."""
-    # Create pipes to simulate stdin/stdout
-    stdin_reader, stdin_writer = anyio.create_memory_object_stream[str](10)
-    
-    async with stdio_server() as (read_stream, write_stream):
-        # Close the input to simulate parent death
-        await stdin_writer.aclose()
-        
-        # Server should detect EOF and exit gracefully
-        with pytest.raises(anyio.EndOfStream):
-            await asyncio.wait_for(read_stream.receive(), timeout=5.0)
+                pass  # Expected - stream closed due to EOF