test: Fix a flaky test

In the modified test file, sleep() is backed by setTimeout(), and some Node runtimes might execute setTimeout callback before the specified delay, meaning that tmi.getValue() will occasionally return `9`. This produces a flaky test. An extra ms leeway in the assertion works round the issue. nodejs/node#10154

Test name updated to reflect that the timer's accuracy does not have single-digit precision

Author: michael-c-snyk

test/metrics.spec.ts

@@ -49,12 +49,15 @@ describe('TimerMetricInstance', () => {
     expect(tmi.getValue()).toBeUndefined;
   });
 
-  it('can time things', async () => {
+  it('can time things with sufficient accuracy', async () => {
     const tmi = new TimerMetricInstance('timer/network_time');
     tmi.start();
     await sleep(10);
     tmi.stop();
-    expect(tmi.getValue()).toBeGreaterThan(9);
+    // Sleep() is backed by setTimeout(), and some Node runtimes might execute setTimeout callback before the specified
+    // delay, meaning that tmi.getValue() will occasionally return `9` at this point. An extra ms leeway in this
+    // assertion works round the issue. https://github.com/nodejs/node/issues/10154
+    expect(tmi.getValue()).toBeGreaterThanOrEqual(9);
   });
 
   it('.start() / .stop() logs start/top and improper use warnings if you try to start/stop it again after stopping it', async () => {