From 4d0aeed4a64b92768c6aad9f3fb3bf054da6f996 Mon Sep 17 00:00:00 2001
From: Joyee Cheung <joyeec9h3@gmail.com>
Date: Wed, 27 Sep 2023 14:00:21 +0200
Subject: [PATCH] test: deflake test-perf-hooks.js

Previously when checking the initial timing we did a lot of checks
after accessing and copying timing.duration and before we check
that timing.duration is roughly the same as performance.now(),
which can lead to flakes if the overhead of the checking is
big enough. Update the test to check timing.duration against
performance.now() as soon as possible when it's copied instead
of computed.
:#

PR-URL: https://github.com/nodejs/node/pull/49892
Refs: https://github.com/nodejs/reliability/issues/676
Reviewed-By: Chemi Atlow <chemi@atlow.co.il>
Reviewed-By: Richard Lau <rlau@redhat.com>
---
 test/sequential/test-perf-hooks.js | 62 +++++++++++++++---------------
 1 file changed, 32 insertions(+), 30 deletions(-)

diff --git a/test/sequential/test-perf-hooks.js b/test/sequential/test-perf-hooks.js
index 5ed9ff22ce2d38..1e11f26571480d 100644
--- a/test/sequential/test-perf-hooks.js
+++ b/test/sequential/test-perf-hooks.js
@@ -41,8 +41,40 @@ const epsilon = 50;
 assert.strictEqual(performance.nodeTiming.name, 'node');
 assert.strictEqual(performance.nodeTiming.entryType, 'node');
 
+// If timing.duration gets copied into the argument instead of being computed
+// via the getter, this should be called right after timing is created.
+function checkNodeTiming(timing) {
+  // Calculate the difference between now() and duration as soon as possible.
+  const now = performance.now();
+  const delta = Math.abs(now - timing.duration);
+
+  log(JSON.stringify(timing, null, 2));
+  // Check that the properties are still reasonable.
+  assert.strictEqual(timing.name, 'node');
+  assert.strictEqual(timing.entryType, 'node');
+
+  // Check that duration is positive and practically the same as
+  // performance.now() i.e. measures Node.js instance up time.
+  assert.strictEqual(typeof timing.duration, 'number');
+  assert(timing.duration > 0, `timing.duration ${timing.duration} <= 0`);
+  assert(delta < 10,
+         `now (${now}) - timing.duration (${timing.duration}) = ${delta} >= ${10}`);
+
+  // Check that the following fields do not change.
+  assert.strictEqual(timing.startTime, initialTiming.startTime);
+  assert.strictEqual(timing.nodeStart, initialTiming.nodeStart);
+  assert.strictEqual(timing.v8Start, initialTiming.v8Start);
+  assert.strictEqual(timing.environment, initialTiming.environment);
+  assert.strictEqual(timing.bootstrapComplete, initialTiming.bootstrapComplete);
+
+  assert.strictEqual(typeof timing.loopStart, 'number');
+  assert.strictEqual(typeof timing.loopExit, 'number');
+}
+
+log('check initial nodeTiming');
 // Copy all the values from the getters.
 const initialTiming = { ...performance.nodeTiming };
+checkNodeTiming(initialTiming);
 
 {
   const {
@@ -87,36 +119,6 @@ const initialTiming = { ...performance.nodeTiming };
          `bootstrapComplete ${bootstrapComplete} >= ${testStartTime}`);
 }
 
-function checkNodeTiming(timing) {
-  // Calculate the difference between now() and duration as soon as possible.
-  const now = performance.now();
-  const delta = Math.abs(now - timing.duration);
-
-  log(JSON.stringify(timing, null, 2));
-  // Check that the properties are still reasonable.
-  assert.strictEqual(timing.name, 'node');
-  assert.strictEqual(timing.entryType, 'node');
-
-  // Check that duration is positive and practically the same as
-  // performance.now() i.e. measures Node.js instance up time.
-  assert.strictEqual(typeof timing.duration, 'number');
-  assert(timing.duration > 0, `timing.duration ${timing.duration} <= 0`);
-  assert(delta < 10,
-         `now (${now}) - timing.duration (${timing.duration}) = ${delta} >= 10`);
-
-  // Check that the following fields do not change.
-  assert.strictEqual(timing.startTime, initialTiming.startTime);
-  assert.strictEqual(timing.nodeStart, initialTiming.nodeStart);
-  assert.strictEqual(timing.v8Start, initialTiming.v8Start);
-  assert.strictEqual(timing.environment, initialTiming.environment);
-  assert.strictEqual(timing.bootstrapComplete, initialTiming.bootstrapComplete);
-
-  assert.strictEqual(typeof timing.loopStart, 'number');
-  assert.strictEqual(typeof timing.loopExit, 'number');
-}
-
-log('check initial nodeTiming');
-checkNodeTiming(initialTiming);
 assert.strictEqual(initialTiming.loopExit, -1);
 
 function checkValue(timing, name, min, max) {