test(agenthub): Add integration tests for metrics endpoint

Ajoute 9 tests d'intégration pour valider l'endpoint /metrics:
- Vérification du format Prometheus (text/plain)
- Présence de toutes les métriques AgentHub custom
- Présence des métriques Node.js par défaut
- Incrémentation correcte des compteurs HTTP

Tous les tests passent ✅

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

test/metrics.test.ts

@@ -0,0 +1,131 @@
+import { describe, it, expect, beforeAll, afterAll } from 'vitest';
+import type { FastifyInstance } from 'fastify';
+import { buildApp } from '../src/app.js';
+import { loadConfig } from '../src/config.js';
+
+describe('Prometheus Metrics', () => {
+  let app: FastifyInstance;
+
+  beforeAll(async () => {
+    const config = loadConfig({
+      NODE_ENV: 'test',
+      LOG_LEVEL: 'fatal',
+      JWT_SECRET: 'test-secret-with-exactly-32chars',
+      FEATURE_MESSAGING_ENABLED: 'false', // Disable WebSocket for metrics test
+    });
+    app = await buildApp({ config });
+  });
+
+  afterAll(async () => {
+    await app.close();
+  });
+
+  it('should expose /metrics endpoint', async () => {
+    const response = await app.inject({
+      method: 'GET',
+      url: '/metrics',
+    });
+
+    expect(response.statusCode).toBe(200);
+    expect(response.headers['content-type']).toContain('text/plain');
+  });
+
+  it('should expose agenthub_agents_connected metric', async () => {
+    const response = await app.inject({
+      method: 'GET',
+      url: '/metrics',
+    });
+
+    expect(response.body).toContain('# HELP agenthub_agents_connected');
+    expect(response.body).toContain('# TYPE agenthub_agents_connected gauge');
+    expect(response.body).toMatch(/agenthub_agents_connected \d+/);
+  });
+
+  it('should expose agenthub_rooms_active metric', async () => {
+    const response = await app.inject({
+      method: 'GET',
+      url: '/metrics',
+    });
+
+    expect(response.body).toContain('# HELP agenthub_rooms_active');
+    expect(response.body).toContain('# TYPE agenthub_rooms_active gauge');
+    expect(response.body).toMatch(/agenthub_rooms_active \d+/);
+  });
+
+  it('should expose agenthub_messages_total metric', async () => {
+    const response = await app.inject({
+      method: 'GET',
+      url: '/metrics',
+    });
+
+    expect(response.body).toContain('# HELP agenthub_messages_total');
+    expect(response.body).toContain('# TYPE agenthub_messages_total counter');
+    expect(response.body).toMatch(/agenthub_messages_total \d+/);
+  });
+
+  it('should expose agenthub_websocket_latency_seconds histogram', async () => {
+    const response = await app.inject({
+      method: 'GET',
+      url: '/metrics',
+    });
+
+    expect(response.body).toContain('# HELP agenthub_websocket_latency_seconds');
+    expect(response.body).toContain('# TYPE agenthub_websocket_latency_seconds histogram');
+    expect(response.body).toContain('agenthub_websocket_latency_seconds_bucket');
+    expect(response.body).toContain('agenthub_websocket_latency_seconds_sum');
+    expect(response.body).toContain('agenthub_websocket_latency_seconds_count');
+  });
+
+  it('should expose agenthub_http_requests_total metric', async () => {
+    const response = await app.inject({
+      method: 'GET',
+      url: '/metrics',
+    });
+
+    expect(response.body).toContain('# HELP agenthub_http_requests_total');
+    expect(response.body).toContain('# TYPE agenthub_http_requests_total counter');
+    // Should have tracked the /metrics request itself
+    expect(response.body).toMatch(/agenthub_http_requests_total\{.*route="\/metrics".*\}/);
+  });
+
+  it('should expose agenthub_http_request_duration_seconds histogram', async () => {
+    const response = await app.inject({
+      method: 'GET',
+      url: '/metrics',
+    });
+
+    expect(response.body).toContain('# HELP agenthub_http_request_duration_seconds');
+    expect(response.body).toContain('# TYPE agenthub_http_request_duration_seconds histogram');
+    expect(response.body).toContain('agenthub_http_request_duration_seconds_bucket');
+  });
+
+  it('should expose default Node.js metrics', async () => {
+    const response = await app.inject({
+      method: 'GET',
+      url: '/metrics',
+    });
+
+    // Check for some default metrics
+    expect(response.body).toContain('agenthub_process_cpu_user_seconds_total');
+    expect(response.body).toContain('agenthub_process_resident_memory_bytes');
+    expect(response.body).toContain('agenthub_nodejs_eventloop_lag_seconds');
+  });
+
+  it('should increment HTTP request metrics on each call', async () => {
+    // Make first call
+    const response1 = await app.inject({
+      method: 'GET',
+      url: '/healthz',
+    });
+    expect(response1.statusCode).toBe(200);
+
+    // Check metrics
+    const metricsResponse = await app.inject({
+      method: 'GET',
+      url: '/metrics',
+    });
+
+    // Should have at least one request to /healthz
+    expect(metricsResponse.body).toMatch(/agenthub_http_requests_total\{.*route="\/healthz".*status_code="200".*\} \d+/);
+  });
+});