Add comprehensive Unicode tests for streamable HTTP transport

- Test Unicode text transmission in both directions (client→server→client)
- Verify Unicode handling in tool descriptions, arguments, and responses
- Verify Unicode handling in prompt descriptions and content
- Test with various Unicode scripts including Cyrillic, Chinese, Japanese,
  Korean, Arabic, Hebrew, Greek, emoji, and special characters
- Use multiprocessing to run server in separate process (avoids ResourceWarnings)
- Follow existing test patterns from test_streamable_http_manager.py

Author: pja-ant

tests/client/test_http_unicode.py

@@ -0,0 +1,247 @@
+"""
+Tests for Unicode handling in streamable HTTP transport.
+
+Verifies that Unicode text is correctly transmitted and received in both directions
+(server→client and client→server) using the streamable HTTP transport.
+"""
+
+from collections.abc import Generator
+
+import pytest
+
+from mcp.client.session import ClientSession
+from mcp.client.streamable_http import streamablehttp_client
+
+# Test constants with various Unicode characters
+UNICODE_TEST_STRINGS = {
+    "cyrillic": "Слой хранилища, где располагаются",
+    "cyrillic_short": "Привет мир",
+    "chinese": "你好世界 - 这是一个测试",
+    "japanese": "こんにちは世界 - これはテストです",
+    "korean": "안녕하세요 세계 - 이것은 테스트입니다",
+    "arabic": "مرحبا بالعالم - هذا اختبار",
+    "hebrew": "שלום עולם - זה מבחן",
+    "greek": "Γεια σου κόσμε - αυτό είναι δοκιμή",
+    "emoji": "Hello 👋 World 🌍 - Testing 🧪 Unicode ✨",
+    "math": "∑ ∫ √ ∞ ≠ ≤ ≥ ∈ ∉ ⊆ ⊇",
+    "accented": "Café, naïve, résumé, piñata, Zürich",
+    "mixed": "Hello世界🌍Привет안녕مرحباשלום",
+    "special": "Line\nbreak\ttab\r\nCRLF",
+    "quotes": '«French» „German" "English" 「Japanese」',
+    "currency": "€100 £50 ¥1000 ₹500 ₽200 ¢99",
+}
+
+
+def run_unicode_server(port: int) -> None:
+    """Run the Unicode test server in a separate process."""
+    # Import inside the function since this runs in a separate process
+    from collections.abc import AsyncGenerator
+    from contextlib import asynccontextmanager
+    from typing import Any
+
+    import uvicorn
+    from starlette.applications import Starlette
+    from starlette.routing import Mount
+
+    import mcp.types as types
+    from mcp.server import Server
+    from mcp.server.streamable_http_manager import StreamableHTTPSessionManager
+    from mcp.types import TextContent, Tool
+
+    # Need to recreate the server setup in this process
+    server = Server(name="unicode_test_server")
+
+    @server.list_tools()
+    async def list_tools() -> list[Tool]:
+        """List tools with Unicode descriptions."""
+        return [
+            Tool(
+                name="echo_unicode",
+                description="🔤 Echo Unicode text - Hello 👋 World 🌍 - Testing 🧪 Unicode ✨",
+                inputSchema={
+                    "type": "object",
+                    "properties": {
+                        "text": {"type": "string", "description": "Text to echo back"},
+                    },
+                    "required": ["text"],
+                },
+            ),
+        ]
+
+    @server.call_tool()
+    async def call_tool(name: str, arguments: dict[str, Any] | None) -> list[TextContent]:
+        """Handle tool calls with Unicode content."""
+        if name == "echo_unicode":
+            text = arguments.get("text", "") if arguments else ""
+            return [
+                TextContent(
+                    type="text",
+                    text=f"Echo: {text}",
+                )
+            ]
+        else:
+            raise ValueError(f"Unknown tool: {name}")
+
+    @server.list_prompts()
+    async def list_prompts() -> list[types.Prompt]:
+        """List prompts with Unicode names and descriptions."""
+        return [
+            types.Prompt(
+                name="unicode_prompt",
+                description="Unicode prompt - Слой хранилища, где располагаются",
+                arguments=[],
+            )
+        ]
+
+    @server.get_prompt()
+    async def get_prompt(name: str, arguments: dict[str, Any] | None) -> types.GetPromptResult:
+        """Get a prompt with Unicode content."""
+        if name == "unicode_prompt":
+            return types.GetPromptResult(
+                messages=[
+                    types.PromptMessage(
+                        role="user",
+                        content=types.TextContent(
+                            type="text",
+                            text="Hello世界🌍Привет안녕مرحباשלום",
+                        ),
+                    )
+                ]
+            )
+        raise ValueError(f"Unknown prompt: {name}")
+
+    # Create the session manager
+    session_manager = StreamableHTTPSessionManager(
+        app=server,
+        json_response=False,  # Use SSE for testing
+    )
+
+    @asynccontextmanager
+    async def lifespan(app: Starlette) -> AsyncGenerator[None, None]:
+        async with session_manager.run():
+            yield
+
+    # Create an ASGI application
+    app = Starlette(
+        debug=True,
+        routes=[
+            Mount("/mcp", app=session_manager.handle_request),
+        ],
+        lifespan=lifespan,
+    )
+
+    # Run the server
+    config = uvicorn.Config(
+        app=app,
+        host="127.0.0.1",
+        port=port,
+        log_level="error",
+    )
+    uvicorn_server = uvicorn.Server(config)
+    uvicorn_server.run()
+
+
+@pytest.fixture
+def unicode_server_port() -> int:
+    """Find an available port for the Unicode test server."""
+    import socket
+
+    with socket.socket() as s:
+        s.bind(("127.0.0.1", 0))
+        return s.getsockname()[1]
+
+
+@pytest.fixture
+def running_unicode_server(unicode_server_port: int) -> Generator[str, None, None]:
+    """Start a Unicode test server in a separate process."""
+    import multiprocessing
+    import socket
+    import time
+
+    proc = multiprocessing.Process(target=run_unicode_server, kwargs={"port": unicode_server_port}, daemon=True)
+    proc.start()
+
+    # Wait for server to be running
+    max_attempts = 20
+    attempt = 0
+    while attempt < max_attempts:
+        try:
+            with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:
+                s.connect(("127.0.0.1", unicode_server_port))
+                break
+        except ConnectionRefusedError:
+            time.sleep(0.1)
+            attempt += 1
+    else:
+        raise RuntimeError(f"Server failed to start after {max_attempts} attempts")
+
+    try:
+        yield f"http://127.0.0.1:{unicode_server_port}"
+    finally:
+        # Clean up - try graceful termination first
+        proc.terminate()
+        proc.join(timeout=2)
+        if proc.is_alive():
+            proc.kill()
+            proc.join(timeout=1)
+
+
+@pytest.mark.anyio
+async def test_streamable_http_client_unicode_tool_call(running_unicode_server: str) -> None:
+    """Test that Unicode text is correctly handled in tool calls via streamable HTTP."""
+    base_url = running_unicode_server
+    endpoint_url = f"{base_url}/mcp"
+
+    async with streamablehttp_client(endpoint_url) as (read_stream, write_stream, _get_session_id):
+        async with ClientSession(read_stream, write_stream) as session:
+            await session.initialize()
+
+            # Test 1: List tools (server→client Unicode in descriptions)
+            tools = await session.list_tools()
+            assert len(tools.tools) == 1
+
+            # Check Unicode in tool descriptions
+            echo_tool = tools.tools[0]
+            assert echo_tool.name == "echo_unicode"
+            assert echo_tool.description is not None
+            assert "🔤" in echo_tool.description
+            assert "👋" in echo_tool.description
+
+            # Test 2: Send Unicode text in tool call (client→server→client)
+            for test_name, test_string in UNICODE_TEST_STRINGS.items():
+                result = await session.call_tool("echo_unicode", arguments={"text": test_string})
+
+                # Verify server correctly received and echoed back Unicode
+                assert len(result.content) == 1
+                content = result.content[0]
+                assert content.type == "text"
+                assert f"Echo: {test_string}" == content.text, f"Failed for {test_name}"
+
+
+@pytest.mark.anyio
+async def test_streamable_http_client_unicode_prompts(running_unicode_server: str) -> None:
+    """Test that Unicode text is correctly handled in prompts via streamable HTTP."""
+    base_url = running_unicode_server
+    endpoint_url = f"{base_url}/mcp"
+
+    async with streamablehttp_client(endpoint_url) as (read_stream, write_stream, _get_session_id):
+        async with ClientSession(read_stream, write_stream) as session:
+            await session.initialize()
+
+            # Test 1: List prompts (server→client Unicode in descriptions)
+            prompts = await session.list_prompts()
+            assert len(prompts.prompts) == 1
+
+            prompt = prompts.prompts[0]
+            assert prompt.name == "unicode_prompt"
+            assert prompt.description is not None
+            assert "Слой хранилища, где располагаются" in prompt.description
+
+            # Test 2: Get prompt with Unicode content (server→client)
+            result = await session.get_prompt("unicode_prompt", arguments={})
+            assert len(result.messages) == 1
+
+            message = result.messages[0]
+            assert message.role == "user"
+            assert message.content.type == "text"
+            assert message.content.text == "Hello世界🌍Привет안녕مرحباשלום"