examples/pytest/test_fibo.py
import mymath

def test_fibo():
    assert mymath.fibo(1) == [1]
    assert mymath.fibo(2) == [1, 1]
    assert mymath.fibo(3) == [1, 1, 2]


examples/pytest/test_fibo.out
$ py.test test_fibo.py 
========================== test session starts ===========================
platform darwin -- Python 2.7.5 -- py-1.4.20 -- pytest-2.5.2
collected 1 items 

test_fibo.py F

================================ FAILURES ================================
_______________________________ test_fibo ________________________________

    def test_fibo():
        assert mymath.fibo(1) == [1]
        assert mymath.fibo(2) == [1, 1]
>       assert mymath.fibo(3) == [1, 1, 2]
E       assert [1, 1, 5] == [1, 1, 2]
E         At index 2 diff: 5 != 2

test_fibo.py:6: AssertionError
======================== 1 failed in 0.01 seconds ========================