fix: fixed test

test/src/channel_preview_test.dart

@@ -42,10 +42,18 @@ void main() {
           user: User(id: 'user-id'),
         ),
       ]);
-      when(channelState.lastMessage).thenReturn(Message(
+      when(channelState.messages).thenReturn([
-        text: 'hello',
+        Message(
-        user: User(id: 'other-user'),
+          text: 'hello',
-      ));
+          user: User(id: 'other-user'),
+        )
+      ]);
+      when(channelState.messagesStream).thenAnswer((i) => Stream.value([
+            Message(
+              text: 'hello',
+              user: User(id: 'other-user'),
+            )
+          ]));
 
       await tester.pumpWidget(MaterialApp(
         home: StreamChat(