Solution: Pytest test this app
import app
def test_swap():
assert app.swap("abcd") == "cdab"
assert app.swap("abc") == "bca"
assert app.swap("abcde") == "cdeab"
assert app.swap("a") == "a"
assert app.swap("") == ""
def test_average():
assert app.average(2, 4) == 3
assert app.average(2, 3) == 2.5
assert app.average(42) == 42
#assert app.average() == 0