Fix tests

Verify that both peers have a connection now that the validation goes
through `SyncingEngine`. Depending on how the tasks are scheduled,
one of them might not have the peer registered in `SyncingEngine` at which
point the test won't make any progress because block announcement received
from an unknown peer is discarded.

Move polling of `ChainSync` at the end of the function so that if a block
announcement causes a block request to be sent, that can be sent in the
same call to `SyncingEngine::poll()`.

client/network/sync/src/engine.rs

@@ -590,10 +590,6 @@ where
 			self.tick_timeout.reset(TICK_TIMEOUT);
 		}
 
-		while let Poll::Ready(result) = self.chain_sync.poll(cx) {
-			self.process_block_announce_validation_result(result);
-		}
-
 		while let Poll::Ready(Some(event)) = self.service_rx.poll_next_unpin(cx) {
 			match event {
 				ToServiceCommand::SetSyncForkRequest(peers, hash, number) => {
@@ -728,6 +724,13 @@ where
 			}
 		}
 
+		// poll `ChainSync` last because of a block announcement was received through the
+		// event stream between `SyncingEngine` and `Protocol` and the validation finished
+		// right after it as queued, the resulting block request (if any) can be sent right away.
+		while let Poll::Ready(result) = self.chain_sync.poll(cx) {
+			self.process_block_announce_validation_result(result);
+		}
+
 		Poll::Pending
 	}
 

client/network/test/src/sync.rs

@@ -414,7 +414,7 @@ async fn can_sync_small_non_best_forks() {
 	// poll until the two nodes connect, otherwise announcing the block will not work
 	futures::future::poll_fn::<(), _>(|cx| {
 		net.poll(cx);
-		if net.peer(0).num_peers() == 0 {
+		if net.peer(0).num_peers() == 0 || net.peer(1).num_peers() == 0 {
 			Poll::Pending
 		} else {
 			Poll::Ready(())