When mobs are summoned using the /summon commands on a team they will not act like they are teamed. Eg: attacks players on same team, snow golems attack zombies on same team, etc. To reproduce summon a (hostile) mob on a team and summon something it would attack ( or put yourself) on the same team. Shulkers are fine though. To make it easier to tell which one is one which team effect them with glowing.
MC-92391
Mobs on teams (except shulkers) do not act teamed.
Resolved
Duplicate
0
Eragon
(Unassigned)
Unconfirmed
mob
Minecraft 15w45a
Retrieved
Thank you for your report.
However, your ticket has been resolved as a duplicate.
This issue has been linked to the original bugreport: MC-46956. You can find or add further information on that report.
Please search before reporting any bugs, as it's likely that one exists already.