import test from 'node:test';
import assert from 'node:assert/strict';
import http from 'node:http';
import { spawn } from 'node:child_process';
import { setTimeout as sleep } from 'node:timers/promises';
import { fileURLToPath } from 'node:url';
import { dirname, join } from 'node:path';
/**
* Integration test for MCP Observability Sidecar
*
* Tests:
* 1. Mock upstream MCP server responds to requests
* 2. Sidecar proxies requests correctly
* 3. Metrics are exported to OTLP collector
*/
test('MCP sidecar proxies requests and exports metrics', async t => {
// ========================================
// Setup mock upstream MCP server
// ========================================
const upstreamPort = 3999;
const upstreamServer = http.createServer((req, res) => {
let body = '';
req.on('data', chunk => { body += chunk; });
req.on('end', () => {
try {
const request = JSON.parse(body);
const response = {
jsonrpc: '2.0',
id: request.id,
result: {
message: 'mock upstream response',
method: request.method,
},
};
res.writeHead(200, { 'Content-Type': 'application/json' });
res.end(JSON.stringify(response));
} catch (err) {
res.writeHead(400).end();
}
});
});
await new Promise<void>(resolve => upstreamServer.listen(upstreamPort, resolve));
t.after(() => upstreamServer.close());
// ========================================
// Setup mock OTLP collector
// ========================================
const received: any[] = [];
let resolveMetric: () => void;
const metricPromise = new Promise<void>(res => { resolveMetric = res; });
const collector = http.createServer((req, res) => {
let body = '';
req.on('data', chunk => { body += chunk; });
req.on('end', () => {
try {
const data = JSON.parse(body);
received.push(data);
resolveMetric?.();
} catch {
received.push(null);
}
res.writeHead(200).end();
});
});
const collectorPort = 4319;
await new Promise<void>(resolve => collector.listen(collectorPort, resolve));
t.after(() => collector.close());
// ========================================
// Start MCP sidecar
// ========================================
const root = dirname(fileURLToPath(import.meta.url));
const projectDir = join(root, '..');
const tsxPath = join(projectDir, 'node_modules', '.bin', 'tsx');
const sidecarPort = 4100;
const serverEnv = {
...process.env,
// Sidecar config
PORT: String(sidecarPort),
HOST: '127.0.0.1',
MCP_UPSTREAM_URL: `http://localhost:${upstreamPort}`,
MCP_UPSTREAM_NAME: 'test-server',
MCP_UPSTREAM_TIMEOUT_MS: '5000',
// OTel config
OTEL_SERVICE_NAME: 'test-sidecar',
OTEL_METRIC_EXPORT_INTERVAL: '200',
OTEL_EXPORTER_OTLP_ENDPOINT: `http://localhost:${collectorPort}`,
OTEL_EXPORTER_OTLP_PROTOCOL: 'http/protobuf',
// Logging
LOG_LEVEL: 'error',
};
const serverProc = spawn(tsxPath, ['src/server.ts'], {
cwd: projectDir,
env: serverEnv,
stdio: ['ignore', 'pipe', 'inherit'],
});
t.after(() => serverProc.kill());
// Wait for sidecar to start
await new Promise<void>((resolve, reject) => {
const timer = setTimeout(() => reject(new Error('sidecar did not start')), 10000);
serverProc.stdout.on('data', data => {
const output = data.toString();
if (output.includes('MCP Observability Sidecar') || output.includes('listening')) {
clearTimeout(timer);
resolve();
}
});
serverProc.on('error', reject);
});
// Give it a moment to fully initialize
await sleep(500);
// ========================================
// Test 1: Health check
// ========================================
const healthRes = await fetch(`http://localhost:${sidecarPort}/health`);
assert.equal(healthRes.status, 200);
const health = await healthRes.json();
assert.equal(health.status, 'healthy');
assert.equal(health.upstream, 'ok');
// ========================================
// Test 2: Proxy MCP request
// ========================================
const mcpRequest = {
jsonrpc: '2.0',
id: 1,
method: 'tools/list',
};
const mcpRes = await fetch(`http://localhost:${sidecarPort}/`, {
method: 'POST',
headers: { 'Content-Type': 'application/json' },
body: JSON.stringify(mcpRequest),
});
assert.equal(mcpRes.status, 200);
const mcpResponse = await mcpRes.json();
assert.equal(mcpResponse.jsonrpc, '2.0');
assert.equal(mcpResponse.id, 1);
assert.ok(mcpResponse.result);
assert.equal(mcpResponse.result.method, 'tools/list');
// ========================================
// Test 3: Verify metrics exported
// ========================================
await Promise.race([metricPromise, sleep(5000)]);
assert.ok(received.length > 0, 'no metrics received from sidecar');
const payload = JSON.stringify(received);
assert.ok(
payload.includes('mcp_requests_total') || payload.includes('mcp_request'),
'expected MCP metric name not found'
);
console.log('✓ Integration test passed: Proxy works and metrics exported');
});
