Jupyter Snippet CB2nd 08_test

2.8. Writing unit tests with py.test

%%writefile first.py
def first(l):
    return l[0]

Overwriting first.py

%%writefile -a first.py

# This is appended to the file.
def test_first():
    assert first([1, 2, 3]) == 1

Appending to first.py

%cat first.py

def first(l):
    return l[0]

# This is appended to the file.
def test_first():
    assert first([1, 2, 3]) == 1

!pytest first.py

============= test session starts ==============
platform linux -- Python 3.6.3, pytest-3.2.1, py-1.4.34
rootdir: ~/git/cookbook-2nd/chapter02_best_practices:
plugins: cov-2.5.1

collecting 0 items
collecting 1 item
collected 1 item

first.py .

=========== 1 passed in 0.00 seconds ===========

%%writefile first.py
def first(l):
    return l[0]

def test_first():
    assert first([1, 2, 3]) == 1
    assert first([]) is None

Overwriting first.py

!pytest first.py

============= test session starts ==============
platform linux -- Python 3.6.3, pytest-3.2.1, py-1.4.34
rootdir: ~/git/cookbook-2nd/chapter02_best_practices:
plugins: cov-2.5.1

collecting 0 items
collecting 1 item
collected 1 item

first.py F

=================== FAILURES ===================
__________________ test_first __________________

    def test_first():
        assert first([1, 2, 3]) == 1
>       assert first([]) is None

first.py:6:
 _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

l = []

    def first(l):
>       return l[0]
E       IndexError: list index out of range

first.py:2: IndexError
=========== 1 failed in 0.02 seconds ===========

%%writefile first.py
def first(l):
    return l[0] if l else None

def test_first():
    assert first([1, 2, 3]) == 1
    assert first([]) is None

Overwriting first.py

!pytest first.py

============= test session starts ==============
platform linux -- Python 3.6.3, pytest-3.2.1, py-1.4.34
rootdir: ~/git/cookbook-2nd/chapter02_best_practices:
plugins: cov-2.5.1

collecting 0 items
collecting 1 item
collected 1 item

first.py .

=========== 1 passed in 0.00 seconds ===========