The pytest-style
testing framework for MCP

Write tests like you already know how

If you know pytest, you know MCP Test Harness. Same conventions, same discovery, same feel. The harness handles server lifecycle, MCP handshake, and session injection.

# tests/test_my_server.py
from mcp_test_harness import assert_tool_call, assert_capabilities

async def test_server_has_tools(mcp_server):
    """Verify the server advertises tool capabilities."""
    await assert_capabilities(mcp_server, {"tools": {}})

async def test_echo_tool(mcp_server):
    """Call the echo tool and check it works."""
    result = await assert_tool_call(
        mcp_server, "echo", {"message": "hello"}
    )
    assert result is not None

async def test_echo_latency(mcp_server):
    """Ensure echo responds within 200ms at p95."""
    await assert_latency(
        mcp_server, "echo", {"message": "hi"},
        max_ms=200, runs=20, aggregate="p95", warmup=3
    )