Fix async tests

packages/nesd/lib/ui/toast/toaster.dart

@@ -14,45 +14,60 @@ Toaster toaster(Ref ref) {
 }
 
 class Toaster {
-  Toaster({required this.state}) {
-    _timer = Timer.periodic(const Duration(milliseconds: 100), (_) {
-      _update();
-    });
-  }
+  Toaster({required this.state});
 
   final ToastState state;
 
-  late final Timer _timer;
+  Timer? _timer;
 
   void dispose() {
-    _timer.cancel();
+    _timer?.cancel();
   }
 
   void send(Toast toast) {
     state.add(toast);
+
+    _scheduleExpiry();
   }
 
   void dismiss(Toast toast) {
     state.remove(toast);
+
+    _scheduleExpiry();
   }
 
-  void _update() {
+  void _scheduleExpiry() {
+    _timer?.cancel();
+    _timer = null;
+
     final top = state.top;
 
     if (top == null) {
       return;
     }
 
-    final lifetime = switch (top.type) {
-      ToastType.info => const Duration(seconds: 3),
-      ToastType.warning => const Duration(seconds: 5),
-      ToastType.error => const Duration(seconds: 8),
-    };
+    final elapsed = DateTime.now().difference(top.createdAt);
+    final remaining = _lifetime(top) - elapsed;
+
+    if (remaining <= Duration.zero) {
+      _onExpiry();
 
-    if (DateTime.now().difference(top.createdAt) > lifetime) {
-      state.pop();
+      return;
     }
+
+    _timer = Timer(remaining, _onExpiry);
   }
+
+  void _onExpiry() {
+    state.pop();
+    _scheduleExpiry();
+  }
+
+  Duration _lifetime(Toast toast) => switch (toast.type) {
+    ToastType.info => const Duration(seconds: 3),
+    ToastType.warning => const Duration(seconds: 5),
+    ToastType.error => const Duration(seconds: 8),
+  };
 }
 
 @riverpod

packages/nesd/test/ui/robot.dart

@@ -1,5 +1,6 @@
 import 'dart:convert';
 import 'dart:io';
+import 'dart:math';
 import 'dart:ui';
 
 import 'package:flutter/services.dart';
@@ -13,6 +14,7 @@ import 'package:nesd/ui/nesd_app.dart';
 import 'package:nesd/ui/settings/settings.dart';
 import 'package:nesd/ui/settings/shared_preferences.dart';
 import 'package:package_info_plus/package_info_plus.dart';
+import 'package:path/path.dart' as path;
 import 'package:shared_preferences/shared_preferences.dart';
 
 import 'base_robot.dart';
@@ -86,6 +88,14 @@ class Robot extends BaseRobot {
     tester.view.physicalSize =
         const Size(1920, 1080) * tester.view.devicePixelRatio;
 
+    final tempDir = _createTempDir();
+
+    addTearDown(() {
+      if (tempDir.existsSync()) {
+        tempDir.deleteSync(recursive: true);
+      }
+    });
+
     await tester.pumpWidget(
       ProviderScope(
         overrides: [
@@ -95,14 +105,22 @@ class Robot extends BaseRobot {
           sharedPreferencesProvider.overrideWithValue(sharedPreferences),
           packageInfoProvider.overrideWithValue(packageInfo),
           filesystemProvider.overrideWithValue(fileSystem),
-          applicationSupportPathProvider.overrideWithValue('/tmp/nesd'),
+          applicationSupportPathProvider.overrideWithValue(tempDir.path),
         ],
         child: const NesdApp(),
       ),
     );
     await tester.pumpAndSettle();
   }
 
+  Directory _createTempDir() {
+    final random = Random().nextInt(1 << 32).toRadixString(36);
+    final dir = Directory(path.join(Directory.systemTemp.path, 'nesd_$random'))
+      ..createSync();
+
+    return dir;
+  }
+
   Future<void> screenshot(String filename) async {
     await tester.runAsync(() async {
       final image = await captureImage(