Add ergonomic Client class for testing MCP servers (#1870)

tests/issues/test_141_resource_templates.py

@@ -1,10 +1,8 @@
 import pytest
 from pydantic import AnyUrl
 
+from mcp import Client
 from mcp.server.fastmcp import FastMCP
-from mcp.shared.memory import (
-    create_connected_server_and_client_session as client_session,
-)
 from mcp.types import (
     ListResourceTemplatesResult,
     TextResourceContents,
@@ -78,10 +76,7 @@ async def test_resource_template_client_interaction():
     def get_user_profile(user_id: str) -> str:
         return f"Profile for user {user_id}"
 
-    async with client_session(mcp._mcp_server) as session:
-        # Initialize the session
-        await session.initialize()
-
+    async with Client(mcp) as session:
         # List available resources
         resources = await session.list_resource_templates()
         assert isinstance(resources, ListResourceTemplatesResult)

tests/issues/test_152_resource_mime_type.py

@@ -3,13 +3,10 @@ import base64
 import pytest
 from pydantic import AnyUrl
 
-from mcp import types
+from mcp import Client, types
 from mcp.server.fastmcp import FastMCP
 from mcp.server.lowlevel import Server
 from mcp.server.lowlevel.helper_types import ReadResourceContents
-from mcp.shared.memory import (
-    create_connected_server_and_client_session as client_session,
-)
 
 pytestmark = pytest.mark.anyio
 
@@ -33,7 +30,7 @@ async def test_fastmcp_resource_mime_type():
         return image_bytes
 
     # Test that resources are listed with correct mime type
-    async with client_session(mcp._mcp_server) as client:
+    async with Client(mcp) as client:
         # List resources and verify mime types
         resources = await client.list_resources()
         assert resources.resources is not None
@@ -91,7 +88,7 @@ async def test_lowlevel_resource_mime_type():
         raise Exception(f"Resource not found: {uri}")  # pragma: no cover
 
     # Test that resources are listed with correct mime type
-    async with client_session(server) as client:
+    async with Client(server) as client:
         # List resources and verify mime types
         resources = await client.list_resources()
         assert resources.resources is not None

tests/issues/test_1574_resource_uri_validation.py

@@ -12,12 +12,9 @@ These tests verify the fix works end-to-end through the JSON-RPC protocol.
 
 import pytest
 
-from mcp import types
+from mcp import Client, types
 from mcp.server.lowlevel import Server
 from mcp.server.lowlevel.helper_types import ReadResourceContents
-from mcp.shared.memory import (
-    create_connected_server_and_client_session as client_session,
-)
 
 pytestmark = pytest.mark.anyio
 
@@ -48,7 +45,7 @@ async def test_relative_uri_roundtrip():
             )
         ]
 
-    async with client_session(server) as client:
+    async with Client(server) as client:
         # List should return the exact URIs we specified
         resources = await client.list_resources()
         uri_map = {r.uri: r for r in resources.resources}
@@ -83,7 +80,7 @@ async def test_custom_scheme_uri_roundtrip():
     async def read_resource(uri: str):
         return [ReadResourceContents(content="data", mime_type="text/plain")]
 
-    async with client_session(server) as client:
+    async with Client(server) as client:
         resources = await client.list_resources()
         uri_map = {r.uri: r for r in resources.resources}
 

tests/issues/test_1754_mime_type_parameters.py

@@ -7,10 +7,8 @@ with parameters like 'text/html;profile=mcp-app' which are valid per RFC 2045.
 import pytest
 from pydantic import AnyUrl
 
+from mcp import Client
 from mcp.server.fastmcp import FastMCP
-from mcp.shared.memory import (
-    create_connected_server_and_client_session as client_session,
-)
 
 pytestmark = pytest.mark.anyio
 
@@ -63,7 +61,7 @@ async def test_mime_type_preserved_in_read_resource():
     def my_widget() -> str:
         return "<html><body>Hello MCP-UI</body></html>"
 
-    async with client_session(mcp._mcp_server) as client:
+    async with Client(mcp) as client:
         # Read the resource
         result = await client.read_resource(AnyUrl("ui://my-widget"))
         assert len(result.contents) == 1

tests/issues/test_188_concurrency.py

@@ -2,8 +2,8 @@ import anyio
 import pytest
 from pydantic import AnyUrl
 
+from mcp import Client
 from mcp.server.fastmcp import FastMCP
-from mcp.shared.memory import create_connected_server_and_client_session as create_session
 
 
 @pytest.mark.anyio
@@ -30,7 +30,7 @@ async def test_messages_are_executed_concurrently_tools():
         call_order.append("trigger_end")
         return "slow"
 
-    async with create_session(server._mcp_server) as client_session:
+    async with Client(server) as client_session:
         # First tool will wait on event, second will set it
         async with anyio.create_task_group() as tg:
             # Start the tool first (it will wait on event)
@@ -70,7 +70,7 @@ async def test_messages_are_executed_concurrently_tools_and_resources():
         call_order.append("resource_end")
         return "slow"
 
-    async with create_session(server._mcp_server) as client_session:
+    async with Client(server) as client_session:
         # First tool will wait on event, second will set it
         async with anyio.create_task_group() as tg:
             # Start the tool first (it will wait on event)