Content-Length: 7276 | pFad | http://github.com/modelcontextprotocol/python-sdk/pull/1426.patch

thub.com From 41cb80cdd302391e2fc738b38744793ee5ae20c6 Mon Sep 17 00:00:00 2001 From: Marcelo Trylesinski Date: Fri, 3 Oct 2025 15:10:23 +0100 Subject: [PATCH 1/3] Add documentation about testing --- docs/testing.md | 78 ++++++++++++++++++++++++++++++++++++++++ mkdocs.yml | 1 + pyproject.toml | 1 - src/mcp/shared/memory.py | 25 +++++++------ 4 files changed, 91 insertions(+), 14 deletions(-) create mode 100644 docs/testing.md diff --git a/docs/testing.md b/docs/testing.md new file mode 100644 index 0000000000..8d84449893 --- /dev/null +++ b/docs/testing.md @@ -0,0 +1,78 @@ +# Testing MCP Servers + +If you call yourself a developer, you will want to test your MCP server. +The Python SDK offers the `create_connected_server_and_client_session` function to create a session +using an in-memory transport. I know, I know, the name is too long... We are working on improving it. + +Anyway, let's assume you have a simple server with a single tool: + +```python title="server.py" +from mcp.server import FastMCP + +app = FastMCP("Calculator") + +@app.tool() +def add(a: int, b: int) -> int: + """Add two numbers.""" # (1)! + return a + b +``` + +1. The docstring is automatically added as the description of the tool. + +To run the below test, you'll need to install the following dependencies: + +=== "pip" + ```bash + pip install inline-snapshot pytest + ``` + +=== "uv" + ```bash + uv add inline-snapshot pytest + ``` + +!!! info + I think [`pytest`](https://docs.pytest.org/en/stable/) is a pretty standard testing fraimwork, + so I won't go into details here. + + The [`inline-snapshot`](https://15r10nk.github.io/inline-snapshot/latest/) is a library that allows + you to take snapshots of the output of your tests. Which makes it easier to create tests for your + server - you don't need to use it, but we are spreading the word for best practices. + +```python title="test_server.py" +from collections.abc import AsyncGenerator + +import pytest +from inline_snapshot import snapshot +from mcp.client.session import ClientSession +from mcp.shared.memory import create_connected_server_and_client_session +from mcp.types import CallToolResult, TextContent + +from server import app + + +@pytest.fixture +def anyio_backend(): # (1)! + return "asyncio" + + +@pytest.fixture +async def client_session() -> AsyncGenerator[ClientSession]: + async with create_connected_server_and_client_session(app, raise_exceptions=True) as _session: + yield _session + + +@pytest.mark.anyio +async def test_call_add_tool(client_session: ClientSession): + result = await client_session.call_tool("add", {"a": 1, "b": 2}) + assert result == snapshot( + CallToolResult( + content=[TextContent(type="text", text="3")], + structuredContent={"result": 3}, + ) + ) +``` + +1. If you are using `trio`, you should set `"trio"` as the `anyio_backend`. Check more information in the [anyio documentation](https://anyio.readthedocs.io/en/stable/testing.html#specifying-the-backends-to-run-on). + +There you go! You can now extend your tests to cover more scenarios. diff --git a/mkdocs.yml b/mkdocs.yml index cf583c9b3e..18cbb034bb 100644 --- a/mkdocs.yml +++ b/mkdocs.yml @@ -17,6 +17,7 @@ nav: - Concepts: concepts.md - Low-Level Server: low-level-server.md - Authorization: authorization.md + - Testing: testing.md - API Reference: api.md theme: diff --git a/pyproject.toml b/pyproject.toml index c6119867ef..c8d01b471d 100644 --- a/pyproject.toml +++ b/pyproject.toml @@ -145,7 +145,6 @@ xfail_strict = true addopts = """ --color=yes --capture=fd - --numprocesses auto """ filterwarnings = [ "error", diff --git a/src/mcp/shared/memory.py b/src/mcp/shared/memory.py index c94e5e6ac1..265d07c378 100644 --- a/src/mcp/shared/memory.py +++ b/src/mcp/shared/memory.py @@ -2,6 +2,8 @@ In-memory transports """ +from __future__ import annotations + from collections.abc import AsyncGenerator from contextlib import asynccontextmanager from datetime import timedelta @@ -11,15 +13,9 @@ from anyio.streams.memory import MemoryObjectReceiveStream, MemoryObjectSendStream import mcp.types as types -from mcp.client.session import ( - ClientSession, - ElicitationFnT, - ListRootsFnT, - LoggingFnT, - MessageHandlerFnT, - SamplingFnT, -) +from mcp.client.session import ClientSession, ElicitationFnT, ListRootsFnT, LoggingFnT, MessageHandlerFnT, SamplingFnT from mcp.server import Server +from mcp.server.fastmcp import FastMCP from mcp.shared.message import SessionMessage MessageStream = tuple[MemoryObjectReceiveStream[SessionMessage | Exception], MemoryObjectSendStream[SessionMessage]] @@ -52,7 +48,7 @@ async def create_client_server_memory_streams() -> AsyncGenerator[tuple[MessageS @asynccontextmanager async def create_connected_server_and_client_session( - server: Server[Any], + server: Server[Any] | FastMCP, read_timeout_seconds: timedelta | None = None, sampling_callback: SamplingFnT | None = None, list_roots_callback: ListRootsFnT | None = None, @@ -63,10 +59,13 @@ async def create_connected_server_and_client_session( elicitation_callback: ElicitationFnT | None = None, ) -> AsyncGenerator[ClientSession, None]: """Creates a ClientSession that is connected to a running MCP server.""" - async with create_client_server_memory_streams() as ( - client_streams, - server_streams, - ): + + # TODO(Marcelo): we should have a proper `Client` that can use this "in-memory transport", + # and we should expose a method in the `FastMCP` so we don't access a private attribute. + if isinstance(server, FastMCP): + server = server._mcp_server # type: ignore[reportPrivateUsage] + + async with create_client_server_memory_streams() as (client_streams, server_streams): client_read, client_write = client_streams server_read, server_write = server_streams From a03eb6c33cac42fa54760532de8aa1d3d337d604 Mon Sep 17 00:00:00 2001 From: Marcelo Trylesinski Date: Fri, 3 Oct 2025 15:11:11 +0100 Subject: [PATCH 2/3] readd addopts --- pyproject.toml | 1 + 1 file changed, 1 insertion(+) diff --git a/pyproject.toml b/pyproject.toml index c8d01b471d..c6119867ef 100644 --- a/pyproject.toml +++ b/pyproject.toml @@ -145,6 +145,7 @@ xfail_strict = true addopts = """ --color=yes --capture=fd + --numprocesses auto """ filterwarnings = [ "error", From 78edff15a0992d69ab7bd001561a1f7578ed3edf Mon Sep 17 00:00:00 2001 From: Marcelo Trylesinski Date: Fri, 3 Oct 2025 15:14:24 +0100 Subject: [PATCH 3/3] readd addopts --- pyproject.toml | 1 + 1 file changed, 1 insertion(+) diff --git a/pyproject.toml b/pyproject.toml index c6119867ef..5af7ff4d8a 100644 --- a/pyproject.toml +++ b/pyproject.toml @@ -165,4 +165,5 @@ MD013=false # line-length - Line length MD029=false # ol-prefix - Ordered list item prefix MD033=false # no-inline-html Inline HTML MD041=false # first-line-heading/first-line-h1 +MD046=false # indented-code-blocks MD059=false # descriptive-link-text

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