def test_powerset_method():
# EmptySet
A = FiniteSet()
pset = A.powerset()
assert len(pset) == 1
assert pset == FiniteSet(S.EmptySet)
# FiniteSets
A = FiniteSet(1, 2)
pset = A.powerset()
assert len(pset) == 2**len(A)
assert pset == FiniteSet(FiniteSet(), FiniteSet(1), FiniteSet(2), A)
# Not finite sets
A = Interval(0, 1)
assert A.powerset() == PowerSet(A)
