From d25f16e8ea9593fdefef87dd259ab9d01a24d736 Mon Sep 17 00:00:00 2001
From: Claude <noreply@anthropic.com>
Date: Fri, 17 Apr 2026 19:15:18 +0000
Subject: [PATCH] test: stabilize macOS runs by lengthening tick defaults

macOS backs fs.watch with FSEvents, which has a ~100-500ms dispatch
cycle and coalesces rapid changes. The current 110ms default tick and
300-400ms beforeEach/afterEach waits race those timings, which is the
main source of macOS-only test flakes (`should aggregate changes while
paused`, the `fast` DirectoryWatcher variant, residual events leaking
between tests, etc.).

- bump the default tick to 260ms on darwin (unchanged elsewhere)
- bump beforeEach quiesce to 700ms and afterEach to 500ms on darwin
- bump the DirectoryWatcher "fast" interval from 50 to 150ms on darwin
  so consecutive writes are not coalesced by FSEvents

Test-only change; no library behavior is affected.
---
 test/DirectoryWatcher.test.js |  6 +++++-
 test/helpers/TestHelper.js    | 13 +++++++++----
 2 files changed, 14 insertions(+), 5 deletions(-)

diff --git a/test/DirectoryWatcher.test.js b/test/DirectoryWatcher.test.js
index 62323f7..21e270e 100644
--- a/test/DirectoryWatcher.test.js
+++ b/test/DirectoryWatcher.test.js
@@ -138,10 +138,14 @@ describe("DirectoryWatcher", () => {
 		});
 	});
 
+	const IS_OSX = require("os").platform() === "darwin";
+
 	/** @type {Record<"slow" | "fast", number>} */
+	// FSEvents coalesces rapid changes, so on macOS the "fast" case needs a
+	// larger interval or consecutive writes will be dropped.
 	const timings = {
 		slow: 300,
-		fast: 50,
+		fast: IS_OSX ? 150 : 50,
 	};
 	for (const name of Object.keys(timings)) {
 		const time = timings[/** @type {keyof typeof timings} */ (name)];
diff --git a/test/helpers/TestHelper.js b/test/helpers/TestHelper.js
index 57ea6cb..d8f8461 100644
--- a/test/helpers/TestHelper.js
+++ b/test/helpers/TestHelper.js
@@ -12,6 +12,8 @@ const writeFileAtomic = require("write-file-atomic");
 
 const watchEventSource = require("../../lib/watchEventSource");
 
+const IS_OSX = require("os").platform() === "darwin";
+
 require("../../lib/getWatcherManager");
 let watcherManagerModule =
 	require.cache[require.resolve("../../lib/getWatcherManager")];
@@ -48,7 +50,10 @@ class TestHelper {
 	 */
 	tick(arg, fn) {
 		// if polling is set, ensure the tick is longer than the polling interval.
-		const defaultTick = (Number(process.env.WATCHPACK_POLLING) || 100) + 10;
+		// On macOS the FSEvents dispatch cycle is ~100-500ms, so use a larger
+		// default tick there to keep fs.watch-based tests stable.
+		const defaultTick =
+			(Number(process.env.WATCHPACK_POLLING) || (IS_OSX ? 250 : 100)) + 10;
 
 		if (typeof arg === "function") {
 			fn = arg;
@@ -66,7 +71,7 @@ class TestHelper {
 	 */
 	before(done) {
 		checkAllWatcherClosed();
-		this.tick(400, () => {
+		this.tick(IS_OSX ? 700 : 400, () => {
 			this.rm(this.testdir);
 			fs.mkdirSync(this.testdir);
 			done();
@@ -88,10 +93,10 @@ class TestHelper {
 				return;
 			}
 			checkAllWatcherClosed();
-			this.tick(300, done);
+			this.tick(IS_OSX ? 500 : 300, done);
 		};
 
-		this.tick(300, () => {
+		this.tick(IS_OSX ? 500 : 300, () => {
 			del();
 		});
 	}