emoji_reaction test: Set up whole ZulipApp, not just MaterialApp

This way, the ReactionChipsList gets our theme extensions and lots
of other stuff for free, so it's more representative. We're about to
add a theme extension for this page, so it's helpful to do this now.

Author: chrisbobbe

test/widgets/emoji_reaction_test.dart

@@ -10,8 +10,9 @@ import 'package:flutter_test/flutter_test.dart';
 import 'package:zulip/api/model/events.dart';
 import 'package:zulip/api/model/model.dart';
 import 'package:zulip/model/store.dart';
+import 'package:zulip/widgets/app.dart';
 import 'package:zulip/widgets/emoji_reaction.dart';
-import 'package:zulip/widgets/store.dart';
+import 'package:zulip/widgets/page.dart';
 
 import '../example_data.dart' as eg;
 import '../flutter_checks.dart';
@@ -46,25 +47,28 @@ void main() {
     }) async {
       final message = eg.streamMessage(reactions: reactions);
 
-      await tester.pumpWidget(
-        MaterialApp(
-          home: Directionality(
-            textDirection: textDirection,
-            child: GlobalStoreWidget(
-              child: PerAccountStoreWidget(
-                accountId: eg.selfAccount.id,
-                child: Center(
-                  child: ColoredBox(
-                    color: Colors.white,
-                    child: SizedBox(
-                      width: width,
-                      child: ReactionChipsList(
-                        messageId: message.id,
-                        reactions: message.reactions!,
-                      )))))))));
-
-      // global store, per-account store
-      await tester.pumpAndSettle();
+      final locale = switch (textDirection) {
+        TextDirection.ltr => const Locale('en'),
+        TextDirection.rtl => const Locale('ar'),
+      };
+      tester.platformDispatcher.localeTestValue = locale;
+      tester.platformDispatcher.localesTestValue = [locale];
+      addTearDown(tester.platformDispatcher.clearLocaleTestValue);
+      addTearDown(tester.platformDispatcher.clearLocalesTestValue);
+
+      await tester.pumpWidget(const ZulipApp());
+      await tester.pump();
+      final navigator = await ZulipApp.navigator;
+      navigator.push(MaterialAccountWidgetRoute(accountId: eg.selfAccount.id, page: Center(
+        child: ColoredBox(
+          color: Colors.white,
+          child: SizedBox(
+            width: width,
+            child: ReactionChipsList(
+              messageId: message.id,
+              reactions: message.reactions!,
+            ))))));
+      await tester.pumpAndSettle(); // global store, per-account store
 
       final reactionChipsList = tester.element(find.byType(ReactionChipsList));
       check(Directionality.of(reactionChipsList)).equals(textDirection);