refactor: Add test_utils::sync()

Add a function that pops a sync message from one Alice's device and receives it on another.

src/test_utils.rs

@@ -1067,6 +1067,13 @@ pub(crate) async fn mark_as_verified(this: &TestContext, other: &TestContext) {
     peerstate.save_to_db(&this.sql).await.unwrap();
 }
 
+/// Pops a sync message from alice0 and receives it on alice1. Should be used after an action on
+/// alice0's side that implies sending a sync message.
+pub(crate) async fn sync(alice0: &TestContext, alice1: &TestContext) {
+    let sync_msg = alice0.pop_sent_msg().await;
+    alice1.recv_msg(&sync_msg).await;
+}
+
 /// Pretty-print an event to stdout
 ///
 /// Done during tests this is captured by `cargo test` and associated with the test itself.