def test_empty(self):
assert avg([]) is None
def test_iterator(self):
it = iter([7, 8, 9])
assert avg(it) == 8
def test_float_result(self):
assert avg([5, 6, 8]) == 19.0 / 3
def test_float_input(self):
assert avg([5.5, 6.5]) == 6
def test_basic(self):
assert avg([1, 2, 3]) == 2