fails:StringIO#<< when passed [Object] writes the passed argument onto self
fails:StringIO#<< when passed [Object] writes the passed argument at the current position
fails:StringIO#<< when passed [Object] pads self with \000 when the current position is after the end
fails:StringIO#<< when passed [Object] taints self's String when the passed argument is tainted
fails:StringIO#<< when passed [Object] tries to convert the passed argument to a String using #to_s
fails:StringIO#<< when self is not writable raises an IOError
fails:StringIO#<< when in append mode appends the passed argument to the end of self, ignoring current position
fails:StringIO#<< when in append mode correctly updates self's position
