Make test randomness repeatable.

Author: davidmorgan

pkgs/watcher/test/directory_watcher/end_to_end_tests.dart

@@ -52,7 +52,7 @@ void endToEndTests({required bool isNative}) {
       }
 
       // Verify for real and fail the test if still not consistent.
-      if (!client.verify(log: true)) {
+      if (true || !client.verify(log: true)) {
         // Write the file operations before the failure to a log, fail the test.
         final logTemp = Directory.systemTemp.createTempSync();
         final fileChangesLogPath = p.join(logTemp.path, 'changes.txt');
@@ -64,7 +64,10 @@ void endToEndTests({required bool isNative}) {
         fail('''
 Failed on run $i.
 Files changes: $fileChangesLogPath
-Client log: $clientLogPath''');
+Client log: $clientLogPath
+
+${messages.map((m) => '$m\n').join('')}
+''');
       }
     }
   });

pkgs/watcher/test/directory_watcher/file_changer.dart

@@ -133,6 +133,7 @@ class FileChanger {
   /// Returns the path to an already-created file, or `null` if none exists.
   String? _randomExistingFilePath() =>
       (Directory(path).listSync(recursive: true).whereType<File>().toList()
+            ..sort((a, b) => a.path.compareTo(b.path))
             ..shuffle(_random))
           .firstOrNull
           ?.path;
@@ -142,6 +143,7 @@ class FileChanger {
   String? _randomExistingDirectoryPath() => (Directory(
         path,
       ).listSync(recursive: true).whereType<Directory>().toList()
+            ..sort((a, b) => a.path.compareTo(b.path))
             ..shuffle(_random))
           .firstOrNull
           ?.path;