import json from typing import Any import pytest from dirty_equals import Contains from fastmcp import FastMCP from fastmcp.client import Client from fastmcp.client.transports import FastMCPTransport from fastmcp.exceptions import ResourceError from fastmcp.server.proxy import FastMCPProxy USERS = [ {"id": "1", "name": "Alice", "active": True}, {"id": "2", "name": "Bob", "active": True}, {"id": "3", "name": "Charlie", "active": False}, ] @pytest.fixture def fastmcp_server(): server = FastMCP("TestServer") # --- Tools --- @server.tool() def greet(name: str) -> str: """Greet someone by name.""" return f"Hello, {name}!" @server.tool() def add(a: int, b: int) -> int: """Add two numbers together.""" return a + b @server.tool() def error_tool(): """This tool always raises an error.""" raise ValueError("This is a test error") # --- Resources --- @server.resource(uri="resource://wave") def wave() -> str: return "👋" @server.resource(uri="data://users") async def get_users() -> list[dict[str, Any]]: return USERS @server.resource(uri="data://user/{user_id}") async def get_user(user_id: str) -> dict[str, Any] | None: return next((user for user in USERS if user["id"] == user_id), None) # --- Prompts --- @server.prompt() def welcome(name: str) -> str: return f"Welcome to FastMCP, {name}!" return server @pytest.fixture async def proxy_server(fastmcp_server): """Fixture that creates a FastMCP proxy server.""" return await FastMCP.as_proxy(Client(transport=FastMCPTransport(fastmcp_server))) async def test_create_proxy(fastmcp_server): """Test that the proxy server properly forwards requests to the original server.""" # Create a client client = Client(transport=FastMCPTransport(fastmcp_server)) server = await FastMCPProxy.from_client(client) assert isinstance(server, FastMCPProxy) assert isinstance(server, FastMCP) assert server.name == "FastMCP" class TestTools: async def test_list_tools(self, proxy_server): tools = proxy_server.list_tools() assert [t.name for t in tools] == Contains("greet", "add", "error_tool") async def test_list_tools_same_as_original(self, fastmcp_server, proxy_server): assert ( await proxy_server._mcp_list_tools() == await fastmcp_server._mcp_list_tools() ) async def test_call_tool_result_same_as_original( self, fastmcp_server: FastMCP, proxy_server: FastMCPProxy ): result = await fastmcp_server.call_tool("greet", {"name": "Alice"}) proxy_result = await proxy_server.call_tool("greet", {"name": "Alice"}) assert result == proxy_result async def test_call_tool_calls_tool(self, proxy_server): proxy_result = await proxy_server.call_tool("add", {"a": 1, "b": 2}) assert proxy_result[0].text == "3" async def test_error_tool_raises_error(self, proxy_server): with pytest.raises(ValueError, match="This is a test error"): await proxy_server.call_tool("error_tool", {}) class TestResources: async def test_list_resources(self, proxy_server): resources = proxy_server.list_resources() assert [r.name for r in resources] == Contains( "data://users", "resource://wave" ) async def test_list_resources_same_as_original(self, fastmcp_server, proxy_server): assert ( await proxy_server._mcp_list_resources() == await fastmcp_server._mcp_list_resources() ) async def test_read_resource(self, proxy_server: FastMCPProxy): result = await proxy_server.read_resource("resource://wave") assert result == "👋" async def test_read_resource_same_as_original(self, fastmcp_server, proxy_server): result = await fastmcp_server.read_resource("resource://wave") proxy_result = await proxy_server.read_resource("resource://wave") assert proxy_result == result async def test_read_json_resource(self, proxy_server: FastMCPProxy): result = await proxy_server.read_resource("data://users") assert json.loads(result) == USERS async def test_read_resource_returns_none_if_not_found(self, proxy_server): with pytest.raises( ResourceError, match="Unknown resource: resource://nonexistent" ): await proxy_server.read_resource("resource://nonexistent") class TestResourceTemplates: async def test_list_resource_templates(self, proxy_server): templates = proxy_server.list_resource_templates() assert [t.name for t in templates] == Contains("get_user") async def test_list_resource_templates_same_as_original( self, fastmcp_server, proxy_server ): result = await fastmcp_server._mcp_list_resource_templates() proxy_result = await proxy_server._mcp_list_resource_templates() assert proxy_result == result @pytest.mark.parametrize("id", [1, 2, 3]) async def test_read_resource_template(self, proxy_server: FastMCPProxy, id: int): result = await proxy_server.read_resource(f"data://user/{id}") assert json.loads(result) == USERS[id - 1] async def test_read_resource_template_same_as_original( self, fastmcp_server, proxy_server ): result = await fastmcp_server.read_resource("data://user/1") proxy_result = await proxy_server.read_resource("data://user/1") assert proxy_result == result class TestPrompts: async def test_list_prompts(self, proxy_server): prompts = proxy_server.list_prompts() assert [p.name for p in prompts] == Contains("welcome") async def test_list_prompts_same_as_original(self, fastmcp_server, proxy_server): assert ( await proxy_server._mcp_list_prompts() == await fastmcp_server._mcp_list_prompts() ) async def test_render_prompt_same_as_original( self, fastmcp_server: FastMCP, proxy_server ): result = await fastmcp_server.get_prompt("welcome", {"name": "Alice"}) proxy_result = await proxy_server.get_prompt("welcome", {"name": "Alice"}) assert proxy_result == result async def test_render_prompt_calls_prompt(self, proxy_server): result = await proxy_server.get_prompt("welcome", {"name": "Alice"}) assert result[0].content.text == "Welcome to FastMCP, Alice!"