Pedantic remark, but PS functions are generally named in verb-noun style.  There is an [approved verb list](http://msdn.microsoft.com/en-us/library/ms714428(v=vs.85).aspx).

In this case, it would be `Test-Administrator` to follow the same convention as `Test-Path`

Also as an FYI, `System.` is unnecessary when using types, so I generally leave it out because it's noise.  I could see why some people would want the namespace though. YMMV