Manchester United have not had a real test yet, what they have succeeded to do is just a two game good performance. This match against Liecester to me isn't a real test either because they are a bigger side. It is expeced they would win Liecester with ease although the league is full of surprises especially when it comes to playing against weaker teams.
Maybe you don't remember when Manchester United beat Liverpool in the previous game, whether it was called a lucky win or we could call it a victory with team quality. What you say is not true at all. Ten Hag had found his best strategy to defeat his opponents. If the 1-0 advantage can be maintained until the long whistle, Manchester United is back on track, which is a team that is full of hope with 3 wins in a row with the current match taking place. Manchester United was stirred up at the start of this season with a lot of rumors and poor performances but look how easy it is for them to turn things around.