MCP Server E2E Testing

How to set up and run end-to-end tests involving MCP tool servers.

Where MCP Config Goes

MCP servers are configured in .qwen/settings.json under mcpServers. This is the only location that works for E2E testing.

Common mistakes that waste time:

• .mcp.json — Claude Code convention, not Qwen Code
• settings.local.json — schema validation rejects mcpServers here
• --mcp-config CLI flag — does not exist

Setup

The CLI needs a git repo to load project settings. Create a temp directory:

mkdir -p /tmp/test-dir && cd /tmp/test-dir && git init -q
mkdir -p .qwen
cat > .qwen/settings.json << 'EOF'
{
  "mcpServers": {
    "my-server": {
      "command": "node",
      "args": ["/tmp/my-mcp-server.js"],
      "trust": true
    }
  }
}
EOF

Run from that directory:

cd /tmp/test-dir && <qwen> "prompt" \
  --approval-mode yolo --output-format json

Writing Test Servers

Use scripts/mcp-test-server.js as a template. It's a zero-dependency JSON-RPC server over stdin/stdout — no npm install needed.

To create a server with custom tools, copy the template and edit the TOOL_DEFINITIONS array and the handleToolCall function. Each tool definition follows the MCP inputSchema format (standard JSON Schema).

Sanity-checking the server

Test the server without the CLI by piping JSON-RPC directly:

node /tmp/my-mcp-server.js << 'EOF'
{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "initialize",
  "params": {
    "protocolVersion": "2024-11-05",
    "capabilities": {},
    "clientInfo": { "name": "test", "version": "1.0" }
  }
}
{"jsonrpc":"2.0","method":"notifications/initialized"}
{"jsonrpc":"2.0","id":2,"method":"tools/list","params":{}}
EOF

Verifying the Server Loaded

Check the type: "system" init message in JSON output:

"mcp_servers": [{"name": "my-server", "status": "connected"}]

If mcp_servers is empty:

• You're not running from the directory containing .qwen/settings.json
• The directory is not a git repo (git init missing)
• The server command/path is wrong (check stderr with 2>&1)