Test a Streamable HTTP server

Use HTTPServer for an MCP endpoint that is already running. The direct test below uses a local deterministic service, so it does not depend on a public endpoint or network service.

Requirements

Use Python 3.10 or newer and install the CLI/project SDK with m3 init and m3 setup. Run the supplied service and test from the HTTP example project. The service listens on loopback port 8765 and needs no credentials.

Start the local MCP service

In terminal one, run the service with the project interpreter selected and reported by m3 setup. When setup created the default .venv, run:

./.venv/bin/python shipping_http_server.py

On Windows with the default .venv, run .\.venv\Scripts\python.exe shipping_http_server.py. If setup selected an active virtual or Conda environment, use that environment's Python command instead.

Keep it running while the test executes. The server exposes the shipping_quote tool at http://127.0.0.1:8765/mcp/.

Connect and assert the response

Save this complete test as tests/test_shipping_http.py:

import pytest

from m3 import MCPTestKit
from m3.types import HTTPServer, TrustLevel

pytestmark = pytest.mark.m3(suite_name="shipping-http")


def test_shipping_quote_over_http() -> None:
    server = HTTPServer(
        name="shipping",
        url="http://127.0.0.1:8765/mcp/",
        trust=TrustLevel.TRUSTED_PRIVATE,
    )
    with MCPTestKit(env={}) as kit, kit.direct(server) as client:
        assert "shipping_quote" in {tool.name for tool in client.list_all_tools()}
        result = client.call_tool("shipping_quote", {"weight_kg": 2, "zone": "local"})

    assert result.is_error is False
    assert result.structured_content == {"amount": 9.0, "currency": "USD"}

In terminal two, from the same project root, run:

m3 test -- tests/test_shipping_http.py

The test checks tool discovery and the structured quote returned by the local service. The explicit TRUSTED_PRIVATE value allows a direct connection to a loopback endpoint; direct HTTPServer values otherwise default to untrusted. Stop the server in terminal one with Ctrl-C when the test is done. M3 owns the client connection; it does not manage the HTTP server process.

Add authentication

For an endpoint that requires authentication, pass static headers on HTTPServer.headers or use a SecretReference for a credential supplied by environment. Keep provider credentials separate from MCP endpoint headers. See test your own server and the HTTPServer reference.