First, you are working in different functionalities separately and you need the team open their minds looking for technical solutions that make the project reach the defined goals.
But this stage has usually a date in the calendar that must finish. In that moment it’s time to communicate all have to change the mentality to close, close and close the initial scope of the application.
This stage at the end of the development phase is usually one with more stress and the communication with all the people of the group is essential to end it. In addition you have the sponsor asking you for dates & results so it adds a little more stress on you.