The Atlassian products Confluence and JIRA provide the feature for impersonation, what means a system administrator has the possiblity to execute the product in context of an other user.
As a system administrator you get users saying "I can't do this", or you have conversations like "you should see this" and the user says "no I can't". You need to be your user to ensure clarity of instructions, and to spot/resolve other kinds of problems, e.g. check permissions what a user can see. Without giving passwords away, how do you do that? Use impersonation. This enables system administrators to become another user (like "su" in Linux), enable setup, testing etc.
Dave Furlani commented
I agree with the need for impersonation so long as Adminstrators can't save results while impersonating as this could be used to skew the results. In a compliance controlled development/test environment, that could lead to trouble.