V. Testing the code
=====================

In this section I show how to integrate unit tests into the ``CI/CD`` pipeline, and 
again we will make use of the ``ci.yml`` file. Personally, I like the ``pytest`` framework,
and that's what I will use in this section.

Setting up the test
************************************

There is only one function to test (``fizz_buzz.py``), and it is quite simple.
I will put the ``test_fizzbuzz.py`` function directly into the root folder. The structure
of the current github project is as follows:
::
    ├── fizzbuzz.py
    ├── .github
    │   └── workflows
    │       └── ci.yml
    ├── .gitignore
    ├── .pre-commit-config.yaml
    ├── README.md
    └── test_fizzbuzz.py

``test_fizzbuzz.py`` contains:
::

    import pytest

    from fizzbuzz import fizz_buzz

    inputs = [3, 5, 15, 4, 10, 115, 7]

    outputs = ["fizz", "buzz", "fizzbuzz", "4", "buzz", "buzz", "7"]


    @pytest.mark.parametrize("inp,out", zip(inputs, outputs))
    def test_fizzbuzz(inp, out):
        assert fizz_buzz(inp) == out


Append the code below to the ``ci.yml`` file:
::
    - name: tests
      run: pytest

Passing the test
***************************

And here is the result:

.. image:: _static/imgs/12_with_pytest.png
   :scale: 50 %
   :align: center

But that's the case when everything is ok. We are happy. 

Failing the test
***************************

Now a new and innovative idea comes to my mind.
Why overcomplicate the code, why do we start from ``15``? Let's 
sort everything again, the code will like so nice! So, we change the ``fizzbuzz`` code
to the following one:
::
    def fizz_buzz(num: int) -> str:
        """This is my great and neat function to solve the famous
        Fizz Buzz problem.
        :param num: That's the number which we want the answer for

        :return: fizz, buzz, fizzbuzz or the number itself
        """
        if num % 3 == 0:
            return "fizz"
        if num % 5 == 0:
            return "buzz"
        if num % 15 == 0:
            return "fizzbuzz"
        return str(num)

Great, let's push and see that one test has failed:

.. image:: _static/imgs/13_failed_test.png
   :scale: 50 %
   :align: center

That is, by introducing unit tests into the ``CI/CD`` pipeline we were able to catch the 
problem before merging pull request into the ``main`` branch.