fastmcp/tests/utilities/test_mcp_config.py

import inspect
from pathlib import Path

from mcp.types import TextContent

from fastmcp.client.client import Client
from fastmcp.client.transports import (
    SSETransport,
    StdioTransport,
    StreamableHttpTransport,
)
from fastmcp.utilities.mcp_config import MCPConfig, RemoteMCPServer, StdioMCPServer


def test_parse_single_stdio_config():
    config = {
        "mcpServers": {
            "test_server": {
                "command": "echo",
                "args": ["hello"],
            }
        }
    }
    mcp_config = MCPConfig.from_dict(config)
    transport = mcp_config.mcpServers["test_server"].to_transport()
    assert isinstance(transport, StdioTransport)
    assert transport.command == "echo"
    assert transport.args == ["hello"]


def test_parse_single_remote_config():
    config = {
        "mcpServers": {
            "test_server": {
                "url": "http://localhost:8000",
            }
        }
    }
    mcp_config = MCPConfig.from_dict(config)
    transport = mcp_config.mcpServers["test_server"].to_transport()
    assert isinstance(transport, StreamableHttpTransport)
    assert transport.url == "http://localhost:8000"


def test_parse_remote_config_with_transport():
    config = {
        "mcpServers": {
            "test_server": {
                "url": "http://localhost:8000",
                "transport": "sse",
            }
        }
    }
    mcp_config = MCPConfig.from_dict(config)
    transport = mcp_config.mcpServers["test_server"].to_transport()
    assert isinstance(transport, SSETransport)
    assert transport.url == "http://localhost:8000"


def test_parse_remote_config_with_url_inference():
    config = {
        "mcpServers": {
            "test_server": {
                "url": "http://localhost:8000/sse",
            }
        }
    }
    mcp_config = MCPConfig.from_dict(config)
    transport = mcp_config.mcpServers["test_server"].to_transport()
    assert isinstance(transport, SSETransport)
    assert transport.url == "http://localhost:8000/sse"


def test_parse_multiple_servers():
    config = {
        "mcpServers": {
            "test_server": {
                "url": "http://localhost:8000/sse",
            },
            "test_server_2": {
                "command": "echo",
                "args": ["hello"],
                "env": {"TEST": "test"},
            },
        }
    }
    mcp_config = MCPConfig.from_dict(config)
    assert len(mcp_config.mcpServers) == 2
    assert isinstance(mcp_config.mcpServers["test_server"], RemoteMCPServer)
    assert isinstance(mcp_config.mcpServers["test_server"].to_transport(), SSETransport)

    assert isinstance(mcp_config.mcpServers["test_server_2"], StdioMCPServer)
    assert isinstance(
        mcp_config.mcpServers["test_server_2"].to_transport(), StdioTransport
    )
    assert mcp_config.mcpServers["test_server_2"].command == "echo"
    assert mcp_config.mcpServers["test_server_2"].args == ["hello"]
    assert mcp_config.mcpServers["test_server_2"].env == {"TEST": "test"}


async def test_multi_client(tmp_path: Path):
    server_script = inspect.cleandoc("""
        from fastmcp import FastMCP

        mcp = FastMCP()

        @mcp.tool()
        def add(a: int, b: int) -> int:
            return a + b

        if __name__ == '__main__':
            mcp.run()
        """)

    script_path = tmp_path / "test.py"
    script_path.write_text(server_script)

    config = {
        "mcpServers": {
            "test_1": {
                "command": "python",
                "args": [str(script_path)],
            },
            "test_2": {
                "command": "python",
                "args": [str(script_path)],
            },
        }
    }

    client = Client(config)

    async with client:
        tools = await client.list_tools()
        assert len(tools) == 2

        result_1 = await client.call_tool("test_1_add", {"a": 1, "b": 2})
        result_2 = await client.call_tool("test_2_add", {"a": 1, "b": 2})
        assert isinstance(result_1[0], TextContent)
        assert result_1[0].text == "3"
        assert isinstance(result_2[0], TextContent)
        assert result_2[0].text == "3"