def test_arithmetic():
    assert ((Interval(1, 3) + (2, 4)) == (1, 4))
    assert (((1, 3) + Interval(2, 4)) == (1, 4))
    assert ((Interval.open(1, 3) + (2, 4)) == Interval.open_closed(1, 4))
    assert (((1, 3) + Interval.open(2, 4)) == Interval.closed_open(1, 4))
def test_arithmetic():
    assert ((Interval(1, 3) + (2, 4)) == (1, 4))
    assert (((1, 3) + Interval(2, 4)) == (1, 4))
    assert ((Interval.open(1, 3) + (2, 4)) == Interval.open_closed(1, 4))
    assert (((1, 3) + Interval.open(2, 4)) == Interval.closed_open(1, 4))