Fix test handling of link timestamps.

pkgs/watcher/lib/src/stat.dart

@@ -16,7 +16,7 @@ MockTimeCallback? _mockTimeCallback;
 /// The OS file modification time has pretty rough granularity (like a few
 /// seconds) which can make for slow tests that rely on modtime. This lets you
 /// replace it with something you control.
-void mockGetModificationTime(MockTimeCallback callback) {
+void mockGetModificationTime(MockTimeCallback? callback) {
   _mockTimeCallback = callback;
 }
 

pkgs/watcher/test/directory_watcher/polling_test.dart

@@ -16,14 +16,26 @@ void main() {
   watcherFactory = (dir) => PollingDirectoryWatcher(dir,
       pollingDelay: const Duration(milliseconds: 100));
 
-  sharedTests();
-
-  test('does not notify if the modification time did not change', () async {
-    writeFile('a.txt', contents: 'before');
-    writeFile('b.txt', contents: 'before');
-    await startWatcher();
-    writeFile('a.txt', contents: 'after', updateModified: false);
-    writeFile('b.txt', contents: 'after');
-    await expectModifyEvent('b.txt');
+  // Filesystem modification times can be low resolution, mock them.
+  group('with mock mtime', () {
+    setUp(enableMockModificationTimes);
+
+    sharedTests();
+
+    test('does not notify if the modification time did not change', () async {
+      writeFile('a.txt', contents: 'before');
+      writeFile('b.txt', contents: 'before');
+      await startWatcher();
+      writeFile('a.txt', contents: 'after', updateModified: false);
+      writeFile('b.txt', contents: 'after');
+      await expectModifyEvent('b.txt');
+    });
+  });
+
+  // Also test with delayed writes and real mtimes.
+  group('with real mtime', () {
+    setUp(enableWaitingForDifferentModificationTimes);
+
+    sharedTests();
   });
 }

pkgs/watcher/test/file_watcher/link_tests.dart

@@ -20,13 +20,25 @@ void linkTests({required bool isNative}) {
   test('notifies when a link is overwritten with an identical file', () async {
     await startWatcher(path: 'link.txt');
     writeFile('link.txt');
-    await expectModifyEvent('link.txt');
+
+    // TODO(davidmorgan): reconcile differences.
+    if (isNative) {
+      await expectNoEvents();
+    } else {
+      await expectModifyEvent('link.txt');
+    }
   });
 
   test('notifies when a link is overwritten with a different file', () async {
     await startWatcher(path: 'link.txt');
     writeFile('link.txt', contents: 'modified');
-    await expectModifyEvent('link.txt');
+
+    // TODO(davidmorgan): reconcile differences.
+    if (isNative) {
+      await expectNoEvents();
+    } else {
+      await expectModifyEvent('link.txt');
+    }
   });
 
   test(
@@ -35,25 +47,15 @@ void linkTests({required bool isNative}) {
       await startWatcher(path: 'link.txt');
       writeFile('target.txt');
 
-      // TODO(davidmorgan): reconcile differences.
-      if (isNative) {
-        await expectModifyEvent('link.txt');
-      } else {
-        await expectNoEvents();
-      }
+      await expectModifyEvent('link.txt');
     },
   );
 
   test('notifies when a link target is modified', () async {
     await startWatcher(path: 'link.txt');
     writeFile('target.txt', contents: 'modified');
 
-    // TODO(davidmorgan): reconcile differences.
-    if (isNative) {
-      await expectModifyEvent('link.txt');
-    } else {
-      await expectNoEvents();
-    }
+    await expectModifyEvent('link.txt');
   });
 
   test('notifies when a link is removed', () async {
@@ -79,21 +81,11 @@ void linkTests({required bool isNative}) {
 
     writeFile('target.txt', contents: 'modified');
 
-    // TODO(davidmorgan): reconcile differences.
-    if (isNative) {
-      await expectModifyEvent('link.txt');
-    } else {
-      await expectNoEvents();
-    }
+    await expectModifyEvent('link.txt');
 
     writeFile('target.txt', contents: 'modified again');
 
-    // TODO(davidmorgan): reconcile differences.
-    if (isNative) {
-      await expectModifyEvent('link.txt');
-    } else {
-      await expectNoEvents();
-    }
+    await expectModifyEvent('link.txt');
   });
 
   test('notifies when a link is moved away', () async {
@@ -145,24 +137,14 @@ void linkTests({required bool isNative}) {
     writeFile('old.txt');
     renameFile('old.txt', 'target.txt');
 
-    // TODO(davidmorgan): reconcile differences.
-    if (isNative) {
-      await expectModifyEvent('link.txt');
-    } else {
-      await expectNoEvents();
-    }
+    await expectModifyEvent('link.txt');
   });
 
   test('notifies when a different file is moved over the target', () async {
     await startWatcher(path: 'link.txt');
     writeFile('old.txt', contents: 'modified');
     renameFile('old.txt', 'target.txt');
 
-    // TODO(davidmorgan): reconcile differences.
-    if (isNative) {
-      await expectModifyEvent('link.txt');
-    } else {
-      await expectNoEvents();
-    }
+    await expectModifyEvent('link.txt');
   });
 }

pkgs/watcher/test/file_watcher/polling_test.dart

@@ -2,6 +2,7 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
+import 'package:test/test.dart';
 import 'package:watcher/watcher.dart';
 
 import '../utils.dart';
@@ -13,7 +14,21 @@ void main() {
   watcherFactory = (file) =>
       PollingFileWatcher(file, pollingDelay: const Duration(milliseconds: 100));
 
-  fileTests(isNative: false);
-  linkTests(isNative: false);
-  startupRaceTests(isNative: false);
+  // Filesystem modification times can be low resolution, mock them.
+  group('with mock mtime', () {
+    setUp(enableMockModificationTimes);
+
+    fileTests(isNative: false);
+    linkTests(isNative: false);
+    startupRaceTests(isNative: false);
+  });
+
+// Also test with delayed writes and real mtimes.
+  group('with real mtime', () {
+    setUp(enableWaitingForDifferentModificationTimes);
+    fileTests(isNative: false);
+    linkTests(isNative: false);
+    // Don't run `startupRaceTests`, polling can't have a race and the test is
+    // too slow on Windows when waiting for modification times.
+  });
 }