examples/pytest/test_fibonacci.py
import mymath

def test_fibonacci():
    assert mymath.fibonacci(1) == 1
    assert mymath.fibonacci(2) == 1
    assert mymath.fibonacci(3) == 2

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

test_fibonacci.py F

=================================== FAILURES ====================================
________________________________ test_fibonacci _________________________________

    def test_fibonacci():
        assert mymath.fibonacci(1) == 1
        assert mymath.fibonacci(2) == 1
>       assert mymath.fibonacci(3) == 2
E       assert 5 == 2
E        +  where 5 = <function fibonacci at 0x10a024500>(3)
E        +    where <function fibonacci at 0x10a024500> = mymath.fibonacci

test_fibonacci.py:6: AssertionError
=========================== 1 failed in 0.02 seconds ============================