Where to find full explanation of PigTest methods

I really need some better documentation to understand the handful of
methods one can call on in pigtest. Reading the headers is not really
helpful.
For example : "Gets an iterator on the content of one alias ... "

I am trying to figure out what I have or can control in a pigunit test
outside of checking the returned output.
Is there a place that has some detailed examples and some clear discussion?

Thanks