Add a way to run tests many times in parallel.

Author: davidmorgan

pkgs/watcher/test/directory_watcher/file_tests.dart

@@ -12,6 +12,12 @@ import 'package:watcher/src/utils.dart';
 import '../utils.dart';
 
 void fileTests() {
+  for (var i = 0; i != runsPerTest; ++i) {
+    _fileTests();
+  }
+}
+
+void _fileTests() {
   test('does not notify for files that already exist when started', () async {
     // Make some pre-existing files.
     writeFile('a.txt');

pkgs/watcher/test/directory_watcher/link_tests.dart

@@ -9,6 +9,12 @@ import 'package:test/test.dart';
 import '../utils.dart';
 
 void linkTests({required bool isNative}) {
+  for (var i = 0; i != runsPerTest; ++i) {
+    _linkTests(isNative: isNative);
+  }
+}
+
+void _linkTests({required bool isNative}) {
   test('notifies when a link is added', () async {
     createDir('targets');
     createDir('links');

pkgs/watcher/test/file_watcher/file_tests.dart

@@ -13,6 +13,12 @@ void fileTests({required bool isNative}) {
     writeFile('file.txt');
   });
 
+  for (var i = 0; i != runsPerTest; ++i) {
+    _fileTests(isNative: isNative);
+  }
+}
+
+void _fileTests({required bool isNative}) {
   test("doesn't notify if the file isn't modified", () async {
     await startWatcher(path: 'file.txt');
     await expectNoEvents();

pkgs/watcher/test/file_watcher/link_tests.dart

@@ -12,6 +12,12 @@ void linkTests({required bool isNative}) {
     writeLink(link: 'link.txt', target: 'target.txt');
   });
 
+  for (var i = 0; i != runsPerTest; ++i) {
+    _linkTests(isNative: isNative);
+  }
+}
+
+void _linkTests({required bool isNative}) {
   test("doesn't notify if nothing is modified", () async {
     await startWatcher(path: 'link.txt');
     await expectNoEvents();

pkgs/watcher/test/utils.dart

@@ -12,6 +12,9 @@ import 'package:test_descriptor/test_descriptor.dart' as d;
 import 'package:watcher/src/stat.dart';
 import 'package:watcher/watcher.dart';
 
+/// Edit this to run fast-running tests many times.
+int runsPerTest = 100;
+
 typedef WatcherFactory = Watcher Function(String directory);
 
 /// Sets the function used to create the watcher.