diff --git a/assets/l10n/app_en.arb b/assets/l10n/app_en.arb
index 26cd786315..4a16fef83a 100644
--- a/assets/l10n/app_en.arb
+++ b/assets/l10n/app_en.arb
@@ -188,6 +188,10 @@
   "@errorBannerDeactivatedDmLabel": {
     "description": "Label text for error banner when sending a message to one or multiple deactivated users."
   },
+  "errorBannerCannotPostInChannelLabel": "You do not have permission to post in this channel.",
+  "@errorBannerCannotPostInChannelLabel": {
+    "description": "Label text for error banner when sending a message in a channel with no posting permission."
+  },
   "composeBoxAttachFilesTooltip": "Attach files",
   "@composeBoxAttachFilesTooltip": {
     "description": "Tooltip for compose box icon to attach a file to the message."
diff --git a/lib/widgets/compose_box.dart b/lib/widgets/compose_box.dart
index 4897b88629..661e526fd1 100644
--- a/lib/widgets/compose_box.dart
+++ b/lib/widgets/compose_box.dart
@@ -999,8 +999,21 @@ class _StreamComposeBoxState extends State<_StreamComposeBox> implements Compose
     super.dispose();
   }
 
+  Widget? _errorBanner(BuildContext context) {
+    final store = PerAccountStoreWidget.of(context);
+    final selfUser = store.users[store.selfUserId]!;
+    final channel = store.streams[widget.narrow.streamId]!;
+    return channel.hasPostingPermission(selfUser, realmWaitingPeriodThreshold: store.realmWaitingPeriodThreshold)
+      ? null : _ErrorBanner(label: ZulipLocalizations.of(context).errorBannerCannotPostInChannelLabel);
+  }
+
   @override
   Widget build(BuildContext context) {
+    final errorBanner = _errorBanner(context);
+    if (errorBanner != null) {
+      return _ComposeBoxContainer(child: errorBanner);
+    }
+
     return _ComposeBoxLayout(
       contentController: _contentController,
       contentFocusNode: _contentFocusNode,
@@ -1072,16 +1085,19 @@ class _FixedDestinationComposeBoxState extends State<_FixedDestinationComposeBox
   }
 
   Widget? _errorBanner(BuildContext context) {
-    if (widget.narrow case DmNarrow(:final otherRecipientIds)) {
-      final store = PerAccountStoreWidget.of(context);
-      final hasDeactivatedUser = otherRecipientIds.any((id) =>
-        !(store.users[id]?.isActive ?? true));
-      if (hasDeactivatedUser) {
-        return _ErrorBanner(label: ZulipLocalizations.of(context)
-          .errorBannerDeactivatedDmLabel);
-      }
+    final store = PerAccountStoreWidget.of(context);
+    switch (widget.narrow) {
+      case TopicNarrow():
+        final selfUser = store.users[store.selfUserId]!;
+        final channel = store.streams[(widget.narrow as TopicNarrow).streamId]!;
+        return channel.hasPostingPermission(selfUser, realmWaitingPeriodThreshold: store.realmWaitingPeriodThreshold)
+          ? null : _ErrorBanner(label: ZulipLocalizations.of(context).errorBannerCannotPostInChannelLabel);
+      case DmNarrow(:final otherRecipientIds):
+        final hasDeactivatedUser = otherRecipientIds.any((id) =>
+          !(store.users[id]?.isActive ?? true));
+        return hasDeactivatedUser ? _ErrorBanner(label: ZulipLocalizations.of(context)
+          .errorBannerDeactivatedDmLabel) : null;
     }
-    return null;
   }
 
   @override
diff --git a/test/widgets/action_sheet_test.dart b/test/widgets/action_sheet_test.dart
index f2a6403edf..9b9735ec32 100644
--- a/test/widgets/action_sheet_test.dart
+++ b/test/widgets/action_sheet_test.dart
@@ -43,7 +43,7 @@ Future<void> setupToMessageActionSheet(WidgetTester tester, {
 
   await testBinding.globalStore.add(eg.selfAccount, eg.initialSnapshot());
   final store = await testBinding.globalStore.perAccount(eg.selfAccount.id);
-  await store.addUser(eg.user(userId: message.senderId));
+  await store.addUsers([eg.selfUser, eg.user(userId: message.senderId)]);
   if (message is StreamMessage) {
     final stream = eg.stream(streamId: message.streamId);
     await store.addStream(stream);
diff --git a/test/widgets/autocomplete_test.dart b/test/widgets/autocomplete_test.dart
index 15c294696e..12396fcdc5 100644
--- a/test/widgets/autocomplete_test.dart
+++ b/test/widgets/autocomplete_test.dart
@@ -76,10 +76,12 @@ Future<Finder> setupToTopicInput(WidgetTester tester, {
   addTearDown(testBinding.reset);
   await testBinding.globalStore.add(eg.selfAccount, eg.initialSnapshot());
   final store = await testBinding.globalStore.perAccount(eg.selfAccount.id);
+  await store.addUser(eg.selfUser);
   final connection = store.connection as FakeApiConnection;
 
   // prepare message list data
   final stream = eg.stream();
+  await store.addStream(stream);
   final message = eg.streamMessage(stream: stream, sender: eg.selfUser);
   connection.prepare(json: GetMessagesResult(
     anchor: message.id,
diff --git a/test/widgets/compose_box_test.dart b/test/widgets/compose_box_test.dart
index db46367499..55b69a35f0 100644
--- a/test/widgets/compose_box_test.dart
+++ b/test/widgets/compose_box_test.dart
@@ -37,6 +37,11 @@ void main() {
     List<User> users = const [],
     List<ZulipStream> streams = const [],
   }) async {
+    if (narrow is ChannelNarrow || narrow is TopicNarrow) {
+      final channelId = narrow is ChannelNarrow ? narrow.streamId : (narrow as TopicNarrow).streamId;
+      assert(streams.any((stream) => stream.streamId == channelId),
+        'Add a channel with "streamId" the same as of $narrow.streamId to the store.');
+    }
     addTearDown(testBinding.reset);
     final account = eg.account(user: selfUser ?? eg.selfUser);
     await testBinding.globalStore.add(account, eg.initialSnapshot(
@@ -188,15 +193,17 @@ void main() {
     }
 
     testWidgets('_StreamComposeBox', (tester) async {
+      final channel = eg.stream();
       final key = await prepareComposeBox(tester,
-        narrow: ChannelNarrow(eg.stream().streamId));
+        narrow: ChannelNarrow(channel.streamId), streams: [channel]);
       checkComposeBoxTextFields(tester, controllerKey: key,
         expectTopicTextField: true);
     });
 
     testWidgets('_FixedDestinationComposeBox', (tester) async {
+      final channel = eg.stream();
       final key = await prepareComposeBox(tester,
-        narrow: TopicNarrow.ofMessage(eg.streamMessage()));
+        narrow: TopicNarrow(channel.streamId, 'topic'), streams: [channel]);
       checkComposeBoxTextFields(tester, controllerKey: key,
         expectTopicTextField: false);
     });
@@ -207,7 +214,8 @@ void main() {
       required void Function(int messageId) prepareResponse,
     }) async {
       final zulipLocalizations = GlobalLocalizations.zulipLocalizations;
-      await prepareComposeBox(tester, narrow: const TopicNarrow(123, 'some topic'));
+      await prepareComposeBox(tester, narrow: const TopicNarrow(123, 'some topic'),
+        streams: [eg.stream(streamId: 123)]);
 
       final contentInputFinder = find.byWidgetPredicate(
         (widget) => widget is TextField && widget.controller is ComposeContentController);
@@ -271,7 +279,9 @@ void main() {
 
     group('attach from media library', () {
       testWidgets('success', (tester) async {
-        final controllerKey = await prepareComposeBox(tester, narrow: ChannelNarrow(eg.stream().streamId));
+        final channel = eg.stream();
+        final controllerKey = await prepareComposeBox(tester,
+          narrow: ChannelNarrow(channel.streamId), streams: [channel]);
         final composeBoxController = controllerKey.currentState!;
 
         // (When we check that the send button looks disabled, it should be because
@@ -326,8 +336,10 @@ void main() {
     });
 
     group('attach from camera', () {
-      testWidgets('success', (tester) async {
-        final controllerKey = await prepareComposeBox(tester, narrow: ChannelNarrow(eg.stream().streamId));
+      testWidgets('succMessageListPageState.narrowess', (tester) async {
+        final channel = eg.stream();
+        final controllerKey = await prepareComposeBox(tester,
+          narrow: ChannelNarrow(channel.streamId), streams: [channel]);
         final composeBoxController = controllerKey.currentState!;
 
         // (When we check that the send button looks disabled, it should be because
@@ -382,8 +394,10 @@ void main() {
     });
   });
 
-  group('compose box in DMs with deactivated users', () {
-    Finder contentFieldFinder() => find.descendant(
+  group('compose box replacing with error banner', () {
+    final zulipLocalizations = GlobalLocalizations.zulipLocalizations;
+
+    Finder inputFieldFinder() => find.descendant(
       of: find.byType(ComposeBox),
       matching: find.byType(TextField));
 
@@ -392,97 +406,258 @@ void main() {
       matching: find.widgetWithIcon(IconButton, icon));
 
     void checkComposeBoxParts({required bool areShown}) {
-      check(contentFieldFinder().evaluate().length).equals(areShown ? 1 : 0);
+      final inputFieldCount = inputFieldFinder().evaluate().length;
+      areShown ? check(inputFieldCount).isGreaterThan(0) : check(inputFieldCount).equals(0);
       check(attachButtonFinder(Icons.attach_file).evaluate().length).equals(areShown ? 1 : 0);
       check(attachButtonFinder(Icons.image).evaluate().length).equals(areShown ? 1 : 0);
       check(attachButtonFinder(Icons.camera_alt).evaluate().length).equals(areShown ? 1 : 0);
     }
 
-    void checkBanner({required bool isShown}) {
-      final bannerTextFinder = find.text(GlobalLocalizations.zulipLocalizations
-        .errorBannerDeactivatedDmLabel);
-      check(bannerTextFinder.evaluate().length).equals(isShown ? 1 : 0);
+    void checkBannerWithLabel(String label, {required bool isShown}) {
+      check(find.text(label).evaluate().length).equals(isShown ? 1 : 0);
     }
 
-    void checkComposeBox({required bool isShown}) {
+    void checkComposeBoxIsShown(bool isShown, {required String bannerLabel}) {
       checkComposeBoxParts(areShown: isShown);
-      checkBanner(isShown: !isShown);
+      checkBannerWithLabel(bannerLabel, isShown: !isShown);
     }
 
-    Future<void> changeUserStatus(WidgetTester tester,
-        {required User user, required bool isActive}) async {
-      await store.handleEvent(RealmUserUpdateEvent(id: 1,
-        userId: user.userId, isActive: isActive));
-      await tester.pump();
-    }
+    group('in DMs with deactivated users', () {
+      void checkComposeBox({required bool isShown}) => checkComposeBoxIsShown(isShown,
+        bannerLabel: zulipLocalizations.errorBannerDeactivatedDmLabel);
 
-    DmNarrow dmNarrowWith(User otherUser) => DmNarrow.withUser(otherUser.userId,
-      selfUserId: eg.selfUser.userId);
+      Future<void> changeUserStatus(WidgetTester tester,
+          {required User user, required bool isActive}) async {
+        await store.handleEvent(RealmUserUpdateEvent(id: 1,
+          userId: user.userId, isActive: isActive));
+        await tester.pump();
+      }
 
-    DmNarrow groupDmNarrowWith(List<User> otherUsers) => DmNarrow.withOtherUsers(
-      otherUsers.map((u) => u.userId), selfUserId: eg.selfUser.userId);
+      DmNarrow dmNarrowWith(User otherUser) => DmNarrow.withUser(otherUser.userId,
+        selfUserId: eg.selfUser.userId);
 
-    group('1:1 DMs', () {
-      testWidgets('compose box replaced with a banner', (tester) async {
-        final deactivatedUser = eg.user(isActive: false);
-        await prepareComposeBox(tester, narrow: dmNarrowWith(deactivatedUser),
-          users: [deactivatedUser]);
-        checkComposeBox(isShown: false);
-      });
+      DmNarrow groupDmNarrowWith(List<User> otherUsers) => DmNarrow.withOtherUsers(
+        otherUsers.map((u) => u.userId), selfUserId: eg.selfUser.userId);
 
-      testWidgets('active user becomes deactivated -> '
-          'compose box is replaced with a banner', (tester) async {
-        final activeUser = eg.user(isActive: true);
-        await prepareComposeBox(tester, narrow: dmNarrowWith(activeUser),
-          users: [activeUser]);
-        checkComposeBox(isShown: true);
+      group('1:1 DMs', () {
+        testWidgets('compose box replaced with a banner', (tester) async {
+          final deactivatedUser = eg.user(isActive: false);
+          await prepareComposeBox(tester, narrow: dmNarrowWith(deactivatedUser),
+            users: [deactivatedUser]);
+          checkComposeBox(isShown: false);
+        });
 
-        await changeUserStatus(tester, user: activeUser, isActive: false);
-        checkComposeBox(isShown: false);
+        testWidgets('active user becomes deactivated -> '
+            'compose box is replaced with a banner', (tester) async {
+          final activeUser = eg.user(isActive: true);
+          await prepareComposeBox(tester, narrow: dmNarrowWith(activeUser),
+            users: [activeUser]);
+          checkComposeBox(isShown: true);
+
+          await changeUserStatus(tester, user: activeUser, isActive: false);
+          checkComposeBox(isShown: false);
+        });
+
+        testWidgets('deactivated user becomes active -> '
+            'banner is replaced with the compose box', (tester) async {
+          final deactivatedUser = eg.user(isActive: false);
+          await prepareComposeBox(tester, narrow: dmNarrowWith(deactivatedUser),
+            users: [deactivatedUser]);
+          checkComposeBox(isShown: false);
+
+          await changeUserStatus(tester, user: deactivatedUser, isActive: true);
+          checkComposeBox(isShown: true);
+        });
       });
 
-      testWidgets('deactivated user becomes active -> '
-          'banner is replaced with the compose box', (tester) async {
-        final deactivatedUser = eg.user(isActive: false);
-        await prepareComposeBox(tester, narrow: dmNarrowWith(deactivatedUser),
-          users: [deactivatedUser]);
-        checkComposeBox(isShown: false);
+      group('group DMs', () {
+        testWidgets('compose box replaced with a banner', (tester) async {
+          final deactivatedUsers = [eg.user(isActive: false), eg.user(isActive: false)];
+          await prepareComposeBox(tester, narrow: groupDmNarrowWith(deactivatedUsers),
+            users: deactivatedUsers);
+          checkComposeBox(isShown: false);
+        });
 
-        await changeUserStatus(tester, user: deactivatedUser, isActive: true);
-        checkComposeBox(isShown: true);
+        testWidgets('at least one user becomes deactivated -> '
+            'compose box is replaced with a banner', (tester) async {
+          final activeUsers = [eg.user(isActive: true), eg.user(isActive: true)];
+          await prepareComposeBox(tester, narrow: groupDmNarrowWith(activeUsers),
+            users: activeUsers);
+          checkComposeBox(isShown: true);
+
+          await changeUserStatus(tester, user: activeUsers[0], isActive: false);
+          checkComposeBox(isShown: false);
+        });
+
+        testWidgets('all deactivated users become active -> '
+            'banner is replaced with the compose box', (tester) async {
+          final deactivatedUsers = [eg.user(isActive: false), eg.user(isActive: false)];
+          await prepareComposeBox(tester, narrow: groupDmNarrowWith(deactivatedUsers),
+            users: deactivatedUsers);
+          checkComposeBox(isShown: false);
+
+          await changeUserStatus(tester, user: deactivatedUsers[0], isActive: true);
+          checkComposeBox(isShown: false);
+
+          await changeUserStatus(tester, user: deactivatedUsers[1], isActive: true);
+          checkComposeBox(isShown: true);
+        });
       });
     });
 
-    group('group DMs', () {
-      testWidgets('compose box replaced with a banner', (tester) async {
-        final deactivatedUsers = [eg.user(isActive: false), eg.user(isActive: false)];
-        await prepareComposeBox(tester, narrow: groupDmNarrowWith(deactivatedUsers),
-          users: deactivatedUsers);
-        checkComposeBox(isShown: false);
+    group('in topic/channel narrow according to channel post policy', () {
+      void checkComposeBox({required bool isShown}) => checkComposeBoxIsShown(isShown,
+        bannerLabel: zulipLocalizations.errorBannerCannotPostInChannelLabel);
+
+      final testCases = [
+        (ChannelPostPolicy.unknown, UserRole.unknown, true),
+        (ChannelPostPolicy.unknown, UserRole.guest, true),
+        (ChannelPostPolicy.unknown, UserRole.member, true),
+        (ChannelPostPolicy.unknown, UserRole.moderator, true),
+        (ChannelPostPolicy.unknown, UserRole.administrator, true),
+        (ChannelPostPolicy.unknown, UserRole.owner, true),
+        (ChannelPostPolicy.any, UserRole.unknown, true),
+        (ChannelPostPolicy.any, UserRole.guest, true),
+        (ChannelPostPolicy.any, UserRole.member, true),
+        (ChannelPostPolicy.any, UserRole.moderator, true),
+        (ChannelPostPolicy.any, UserRole.administrator, true),
+        (ChannelPostPolicy.any, UserRole.owner, true),
+        (ChannelPostPolicy.fullMembers, UserRole.unknown, true),
+        (ChannelPostPolicy.fullMembers, UserRole.guest, false),
+        (ChannelPostPolicy.fullMembers, UserRole.member, true),
+        (ChannelPostPolicy.fullMembers, UserRole.moderator, true),
+        (ChannelPostPolicy.fullMembers, UserRole.administrator, true),
+        (ChannelPostPolicy.fullMembers, UserRole.owner, true),
+        (ChannelPostPolicy.moderators, UserRole.unknown, true),
+        (ChannelPostPolicy.moderators, UserRole.guest, false),
+        (ChannelPostPolicy.moderators, UserRole.member, false),
+        (ChannelPostPolicy.moderators, UserRole.moderator, true),
+        (ChannelPostPolicy.moderators, UserRole.administrator, true),
+        (ChannelPostPolicy.moderators, UserRole.owner, true),
+        (ChannelPostPolicy.administrators, UserRole.unknown, true),
+        (ChannelPostPolicy.administrators, UserRole.guest, false),
+        (ChannelPostPolicy.administrators, UserRole.member, false),
+        (ChannelPostPolicy.administrators, UserRole.moderator, false),
+        (ChannelPostPolicy.administrators, UserRole.administrator, true),
+        (ChannelPostPolicy.administrators, UserRole.owner, true),
+      ];
+
+      for (final testCase in testCases) {
+        final (ChannelPostPolicy policy, UserRole role, bool canPost) = testCase;
+
+        testWidgets('"${role.name}" user ${canPost ? 'can' : "can't"} post in channel with "${policy.name}" policy', (tester) async {
+          final selfUser = eg.user(role: role);
+          await prepareComposeBox(tester,
+            narrow: const ChannelNarrow(1),
+            selfUser: selfUser,
+            streams: [eg.stream(streamId: 1, channelPostPolicy: policy)],
+          );
+          checkComposeBox(isShown: canPost);
+        });
+
+        testWidgets('"${role.name}" user ${canPost ? 'can' : "can't"} post in topic with "${policy.name}" channel policy', (tester) async {
+          final selfUser = eg.user(role: role);
+          await prepareComposeBox(tester,
+            narrow: const TopicNarrow(1, 'topic'),
+            selfUser: selfUser,
+            streams: [eg.stream(streamId: 1, channelPostPolicy: policy)],
+          );
+          checkComposeBox(isShown: canPost);
+        });
+
+      }
+
+      group('only "full member" user can post in channel with "fullMembers" policy', (){
+        testWidgets('"full member" -> can post in channel', (tester) async {
+          final selfUser = eg.user(role: UserRole.member,
+            dateJoined: DateTime.now().subtract(const Duration(days: 30)).toIso8601String());
+          await prepareComposeBox(tester,
+            narrow: const ChannelNarrow(1),
+            selfUser: selfUser,
+            daysToBecomeFullMember: 30,
+            streams: [eg.stream(streamId: 1, channelPostPolicy: ChannelPostPolicy.fullMembers)],
+          );
+          checkComposeBox(isShown: true);
+        });
+
+        testWidgets('not a "full member" -> cannot post in channel', (tester) async {
+          final selfUser = eg.user(role: UserRole.member,
+            dateJoined: DateTime.now().subtract(const Duration(days: 29)).toIso8601String());
+          await prepareComposeBox(tester,
+            narrow: const ChannelNarrow(1),
+            selfUser: selfUser,
+            daysToBecomeFullMember: 30,
+            streams: [eg.stream(streamId: 1, channelPostPolicy: ChannelPostPolicy.fullMembers)],
+          );
+          checkComposeBox(isShown: false);
+        });
       });
 
-      testWidgets('at least one user becomes deactivated -> '
-          'compose box is replaced with a banner', (tester) async {
-        final activeUsers = [eg.user(isActive: true), eg.user(isActive: true)];
-        await prepareComposeBox(tester, narrow: groupDmNarrowWith(activeUsers),
-          users: activeUsers);
+      Future<void> changeUserRole(WidgetTester tester,
+          {required User user, required UserRole role}) async {
+        await store.handleEvent(RealmUserUpdateEvent(id: 1,
+          userId: user.userId, role: role));
+        await tester.pump();
+      }
+
+      Future<void> changeChannelPolicy(WidgetTester tester,
+          {required ZulipStream channel, required ChannelPostPolicy policy}) async {
+        await store.handleEvent(eg.channelUpdateEvent(channel,
+          property: ChannelPropertyName.channelPostPolicy, value: policy));
+        await tester.pump();
+      }
+
+      testWidgets('user role decreases -> compose box is replaced with the banner', (tester) async {
+        final selfUser = eg.user(role: UserRole.administrator);
+        await prepareComposeBox(tester,
+          narrow: const ChannelNarrow(1),
+          selfUser: selfUser,
+          streams: [eg.stream(streamId: 1, channelPostPolicy: ChannelPostPolicy.administrators)],
+        );
         checkComposeBox(isShown: true);
 
-        await changeUserStatus(tester, user: activeUsers[0], isActive: false);
+        await changeUserRole(tester, user: selfUser, role: UserRole.moderator);
+        checkComposeBox(isShown: false);
+      });
+
+      testWidgets('user role increases -> banner is replaced with the compose box', (tester) async {
+        final selfUser = eg.user(role: UserRole.guest);
+        await prepareComposeBox(tester,
+          narrow: const ChannelNarrow(1),
+          selfUser: selfUser,
+          streams: [eg.stream(streamId: 1, channelPostPolicy: ChannelPostPolicy.moderators)],
+        );
         checkComposeBox(isShown: false);
+
+        await changeUserRole(tester, user: selfUser, role: UserRole.administrator);
+        checkComposeBox(isShown: true);
       });
 
-      testWidgets('all deactivated users become active -> '
-          'banner is replaced with the compose box', (tester) async {
-        final deactivatedUsers = [eg.user(isActive: false), eg.user(isActive: false)];
-        await prepareComposeBox(tester, narrow: groupDmNarrowWith(deactivatedUsers),
-          users: deactivatedUsers);
+      testWidgets('channel policy becomes stricter -> compose box is replaced with the banner', (tester) async {
+        final selfUser = eg.user(role: UserRole.guest);
+        final channel = eg.stream(streamId: 1, channelPostPolicy: ChannelPostPolicy.any);
+        await prepareComposeBox(tester,
+          narrow: const ChannelNarrow(1),
+          selfUser: selfUser,
+          streams: [channel],
+        );
+        checkComposeBox(isShown: true);
+
+        await changeChannelPolicy(tester, channel: channel, policy: ChannelPostPolicy.fullMembers);
         checkComposeBox(isShown: false);
+      });
 
-        await changeUserStatus(tester, user: deactivatedUsers[0], isActive: true);
+      testWidgets('channel policy becomes less strict -> banner is replaced with the compose box', (tester) async {
+        final selfUser = eg.user(role: UserRole.moderator);
+        final channel = eg.stream(streamId: 1, channelPostPolicy: ChannelPostPolicy.administrators);
+        await prepareComposeBox(tester,
+          narrow: const ChannelNarrow(1),
+          selfUser: selfUser,
+          streams: [channel],
+        );
         checkComposeBox(isShown: false);
 
-        await changeUserStatus(tester, user: deactivatedUsers[1], isActive: true);
+        await changeChannelPolicy(tester, channel: channel, policy: ChannelPostPolicy.moderators);
         checkComposeBox(isShown: true);
       });
     });
diff --git a/test/widgets/message_list_test.dart b/test/widgets/message_list_test.dart
index bfe26444de..028c52744e 100644
--- a/test/widgets/message_list_test.dart
+++ b/test/widgets/message_list_test.dart
@@ -100,7 +100,8 @@ void main() {
     testWidgets('MessageListPageState.narrow', (tester) async {
       final stream = eg.stream();
       await setupMessageListPage(tester, narrow: ChannelNarrow(stream.streamId),
-        messages: [eg.streamMessage(stream: stream, content: "<p>a message</p>")]);
+        messages: [eg.streamMessage(stream: stream, content: "<p>a message</p>")],
+        streams: [stream]);
       final state = MessageListPage.ancestorOf(tester.element(find.text("a message")));
       check(state.narrow).equals(ChannelNarrow(stream.streamId));
     });
@@ -108,7 +109,8 @@ void main() {
     testWidgets('composeBoxController finds compose box', (tester) async {
       final stream = eg.stream();
       await setupMessageListPage(tester, narrow: ChannelNarrow(stream.streamId),
-        messages: [eg.streamMessage(stream: stream, content: "<p>a message</p>")]);
+        messages: [eg.streamMessage(stream: stream, content: "<p>a message</p>")],
+        streams: [stream]);
       final state = MessageListPage.ancestorOf(tester.element(find.text("a message")));
       check(state.composeBoxController).isNotNull();
     });