test(backend): expand helper and media coverage

Backend/tests/metrics.test.ts

@@ -0,0 +1,26 @@
+import { describe, expect, test } from 'bun:test';
+
+import { getAllMetrics, incrementMetric } from '../observability/metrics';
+
+describe('observability metrics', () => {
+  test('initializes and increments named counters', () => {
+    const metricName = `requests_${Date.now()}`;
+
+    incrementMetric(metricName);
+    incrementMetric(metricName, 2);
+
+    expect(getAllMetrics()[metricName]).toBe(3);
+  });
+
+  test('tracks multiple counters independently', () => {
+    const metricA = `camera_${Date.now()}_a`;
+    const metricB = `camera_${Date.now()}_b`;
+
+    incrementMetric(metricA, 5);
+    incrementMetric(metricB, 2);
+
+    const metrics = getAllMetrics();
+    expect(metrics[metricA]).toBe(5);
+    expect(metrics[metricB]).toBe(2);
+  });
+});