fails:IO#gets returns the next line of string that were separated by $/
fails:IO#gets assigns the returned line to $_
fails:IO#gets returns the entire content if the separator is nil
fails:IO#gets returns the next paragraph if the separator's length is 0
fails:IO#gets fails on cloned opened streams
fails:IO#gets accepts an integer as first parameter to limit the output's size
fails:IO#gets accepts an integer as second parameter to limit the output's size
fails:IO#gets accepts an integer as limit parameter which is smaller than IO size
fails:IO#gets accepts an integer as limit parameter which is same as IO size
fails:IO#gets accepts an integer as limit parameter which is greater than IO size
