A role as a new manager or team leader can be challenging at the best of times and more so if you have been appointed internally and have to manage people who were previously your peers. The advantages are that you're familiar with the job, have a good idea of the ups and downs of the position and know your senior managers.
However, if you are appointed internally, be prepared for some hurdles. Most of them would apply to any new manager, but because you know the people, the challenges can seem more personal.
In any team there will be a period of testing and of clarifying where the boundaries are. Are you going to let your team go home early? How fussy are you going to be about deadlines? Because your staff know you, this may be expressed more informally than you expect: "You'll let us go home early on Fridays, won't you?" or "Don't be a stickler for deadlines like so-and-so used to be".
Sometimes staff challenge you personally with comments such as "You've changed, you know", or "Now you're one of the bosses, I bet you'll forget what month end is like".
Because they knew you as a peer, your staff know what buttons to push to get a reaction. This is not done deliberately, but more to check out how the team is going to function under your leadership.