msglist test: Move marker message back and forth.

Previously, messageWithMarker already has its new topic in the message
list when initialized. A subsequent event that moves the message from
elsewhere to said topic does not logically make sense. This fixed that
by moving the message back and forth.

We can't simply move the message from elsewhere because we need to
record the initial rects of the messages.

Signed-off-by: Zixuan James Li <[email protected]>

Author: PIG208

test/widgets/message_list_test.dart

@@ -1019,20 +1019,25 @@ void main() {
 
     testWidgets('edit state updates do not affect layout', (WidgetTester tester) async {
       final messages = [
-        eg.streamMessage(),
+        eg.streamMessage(topic: 'orig'),
         eg.streamMessage(
+          topic: 'orig',
           reactions: [eg.unicodeEmojiReaction, eg.realmEmojiReaction],
           flags: [MessageFlag.starred]),
-        eg.streamMessage(),
+        eg.streamMessage(topic: 'orig'),
       ];
       final StreamMessage messageWithMarker = messages[1];
       await setupMessageListPage(tester, messages: messages);
       final rectsBefore = captureMessageRects(tester, messages, messageWithMarker);
       checkMarkersCount(edited: 0, moved: 0);
 
-      // TODO(#150): [messageWithMarker]'s topic in store is inconsistent with the event. This will be fixed soon.
-      await store.handleEvent(eg.updateMessageEventMoveTo(
-        origTopic: 'old', newMessages: [messageWithMarker]));
+      await store.handleEvent(eg.updateMessageEventMoveFrom(
+        origMessages: [store.messages[messageWithMarker.id] as StreamMessage],
+        newTopic: 'new'));
+      await tester.pump();
+      await store.handleEvent(eg.updateMessageEventMoveFrom(
+        origMessages: [store.messages[messageWithMarker.id] as StreamMessage],
+        newTopic: 'orig'));
       await tester.pump();
       check(captureMessageRects(tester, messages, messageWithMarker))
         .deepEquals(rectsBefore);