def test_kwargs():
source = Stream()
def f(acc, x, y=None):
acc = acc + x + y
return acc
L = source.scan(f, y=10).sink_to_list()
for i in range(3):
source.emit(i)
assert L == [0, 11, 23]
def test_scan():
source = Stream()
def f(acc, i):
acc = acc + i
return acc, acc
L = source.scan(f, returns_state=True).sink_to_list()
for i in range(3):
source.emit(i)
assert L == [0, 1, 3]
