def test_union():
a = Stream()
b = Stream()
c = Stream()
L = a.union(b, c).sink_to_list()
a.emit(1)
assert L == [1]
b.emit(2)
assert L == [1, 2]
a.emit(3)
assert L == [1, 2, 3]
c.emit(4)
assert L == [1, 2, 3, 4]
def test_multi_connect():
source0 = Stream()
source1 = Stream()
source_downstream = source0.union(source1)
# connect assumes this default behaviour
# of stream initialization
assert not source_downstream.downstreams
# initialize the second stream to connect to
source_upstream = Stream()
sout = source_downstream.map(lambda x: x + 1)
L = list()
sout = sout.map(L.append)
source_upstream.connect(source_downstream)
source_upstream.emit(2)
source_upstream.emit(4)
assert L == [3, 5]