Add waiting for WS event

Author: sierpinskid

Assets/Plugins/StreamChat/Tests/StatefulClient/ChannelsTests.cs

@@ -636,10 +636,10 @@ private async Task When_sending_message_to_frozen_channel_expect_error_message_r
             Assert.AreNotEqual(StreamMessageType.Error, lastNormalMessage.Type);
 
             await channel.FreezeAsync();
+            await WaitWhileFalseAsync(() => channel.Frozen);
             Assert.IsTrue(channel.Frozen);
 
             await channel.SendNewMessageAsync("MessageAfterFrozenChannel");
-
             var lastMessage = channel.Messages.LastOrDefault();
 
             Assert.IsNotNull(lastMessage);