def test_zip_first():
a = Stream()
b = Stream()
c = a.zip(b).starmap(op.sub)
d = a.zip(b, first=True).starmap(op.add)
L = c.union(d).sink_to_list()
a.emit(1)
b.emit(1)
assert L == [2, 0]
def test_combine_latest_first():
a = Stream()
b = Stream()
c = a.zip(b)
z = c.starmap(op.add)
zz = z.combine_latest(b, emit_on=0, first=b)
L = zz.sink_to_list()
a.emit(1)
b.emit(1)
assert len(L) == 1
def make_c():
out_a = Stream()
out_b = Stream()
out_c = out_a.zip(out_b).map(sum)
return {"out_a": out_a, "out_b": out_b, "out_c": out_c}