>>> from fever import fever_merge_sort

>>> n = fever_merge_sort('fev1.csv', 'fev2.csv', 'fevout.csv')
>>> with open('fevout.csv', 'r') as fref, open('fev1+2ord.csv', 'r') as f:
... 	l = f.readline()
... 	lref = fref.readline()
... 	while l != '' and lref == l:
... 		l = f.readline()
... 		lref = fref.readline()
... 	oeq = lref == l == ''

>>> n == 10 and oeq
True

>>> n = fever_merge_sort('fev3.csv', 'fev4.csv', 'fevout.csv')
>>> with open('fevout.csv', 'r') as fref, open('fev3+4ord.csv', 'r') as f:
... 	l = f.readline()
... 	lref = fref.readline()
... 	while l != '' and lref == l:
... 		l = f.readline()
... 		lref = fref.readline()
... 	oeq = lref == l == ''
>>> n == 8 and oeq
True