Drop uvicorn from test suite

[Kludex]

We should be using httpx.AsyncClient with httpx.ASGITransport.

[jeevakumar-m]

could you pls give more insights on this , happy to work on this

[Kludex]

The idea is to not have Uvicorn running on the test suite, it's to use the ASGITransport to "run as the server".

[jeevakumar-m]

Ok got it thanks , it needs to be updated for all the applicable tests under folder named -> 'tests'. Could you please assign this task

[knotseaborg]

@jeevakumar-m Any success with this issue?

I'm running into ResourceWarning: Unclosed <MemoryObjectReceiveStream at xxxxxx> when testing test_streamablehttp_client-like functions in test_streamable_http.py with ASGITransport.

For the tests, I passed a client factory which returns httpx.AsyncClient wired with httpx.ASGITransport to streamablehttp_client (referenced below).

https://github.com/modelcontextprotocol/python-sdk/blob/679b22970e12b8eec3897108ac7d6b0624809b9e/src/mcp/client/streamable_http.py#L441-L449

[bjoaquinc]

Hello. I am a new contributor and picked up this issue as my first task.

I started implementing it and wanted to check if I have the right understanding. ASGITransport works well for normal request/response tests, but it does not support streaming. It buffers until the application completes, so SSE, WebSockets, and other long-lived streams do not behave correctly. MCP relies on SSE and web socket functionality for testing, so those tests still appear to require a real server such as uvicorn.

I also tried StreamingASGITransport in src/mcp/server/streaming_asgi_transport.py here for SSE tests, but I encountered resource and event loop cleanup issues (for example, resource busy and event loop closed errors). It does not currently seem like a drop-in replacement for uvicorn for streaming tests.

Before I continue, can you confirm whether the intended approach for this issue is:

• Use ASGITransport for standard HTTP tests
• Keep uvicorn for SSE and streaming tests
• Document why both are required and reference the upstream issues

I wanted to check that I am aligned with the intended direction before submitting a PR. Thank you.

[Kludex]

We should implement the transport on our side, if it can't handle stream. Uvicorn should be dropped from the test suite. Maybe a good first step is to actually implement that transport.

[bjoaquinc]

@Kludex Ok noted on this, thanks. I'll look into how to improve StreamingASGITransport so that it can be used as a drop in replacement for uvicorn in streaming tests.