test [nfc]: Allow overriding original stream and add checks.

Sometimes it is more convenient to override the original stream ID when
we also need to prepare responses for the fake API connection.

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

Author: PIG208

test/example_data.dart

@@ -465,13 +465,17 @@ UpdateMessageEvent updateMessageEditEvent(
 
 UpdateMessageEvent updateMessageMoveEvent(
   List<Message> messages, {
+  int? origStreamId,
   int? newStreamId,
   String? origTopic,
   String? newTopic,
   String? origContent,
   String? newContent,
 }) {
   assert(messages.isNotEmpty);
+  assert(origTopic != null, 'origTopic required for a message move');
+  assert(newTopic != null, 'newTopic required for a message move');
+
   final origMessage = messages[0];
   final messageId = origMessage.id;
   return UpdateMessageEvent(
@@ -482,7 +486,7 @@ UpdateMessageEvent updateMessageMoveEvent(
     messageIds: messages.map((message) => message.id).toList(),
     flags: origMessage.flags,
     editTimestamp: 1234567890, // TODO generate timestamp
-    origStreamId: origMessage is StreamMessage ? origMessage.streamId : null,
+    origStreamId: origStreamId ?? (origMessage is StreamMessage ? origMessage.streamId : null),
     newStreamId: newStreamId,
     propagateMode: null,
     origTopic: origTopic,