Add more tests for the powerset() recipe.

git-svn-id: http://svn.python.org/projects/python/trunk@69023 6015fed2-1504-0410-9fe1-9d1591cc4771

Author: raymond.hettinger

Lib/test/test_itertools.py

@@ -1491,6 +1491,12 @@ def __init__(self, newarg=None, *args):
 >>> list(powerset([1,2,3]))
 [(), (1,), (2,), (3,), (1, 2), (1, 3), (2, 3), (1, 2, 3)]
 
+>>> all(len(list(powerset(range(n)))) == 2**n for n in range(18))
+True
+
+>>> list(powerset('abcde')) == sorted(sorted(set(powerset('abcde'))), key=len)
+True
+
 >>> list(unique_everseen('AAAABBBCCDAABBB'))
 ['A', 'B', 'C', 'D']