I don't think Arsenal are too pleased with their win, like many they were just testing tactics and some players, everyone should realise that's what pre-season matches are for, not to satisfy their egos with wins. Most teams don't even put half of their main squad on the pitch in such matches. But it's definitely worth saying that Arsenal are feeling good about themselves
The match was very interesting to watch despite it being a pre season match. Alonso wanted to defeat Arsenal while Arteta also wanted to the same, and they both put their best squads in the game which resulted to this trashing 4-1 defeat at Emirate stadium.
If you watch the match, you will see that almost all Alonso’s first team players start because he wanted a win either. It is a pre season game and it have showed how well prepared Arsenal is as well as Leverkusen because they both try in the game.
Apparently Liverkusen wanted to start their new winning streak, but it didn't work out. In general, nothing terrible happened, both teams learnt some lesson from it. EPL matches will start tomorrow, and the day after tomorrow Arsenal will play their first match and I think it is very important to start the season with a win, not so much for the position in the standings, but for the morale-booster