Test Driven

Development Demo with PyTest

TDD

Discussed in hpr4075

Write a new test and run it. It should fail.

Write the minimal code that will pass the test

Optionally - refactor the code while ensure the tests continue to

pass

PyTest

Framework for writing software tests with python

Normally used to test python projects, but could test any software

that python can launch return input.

if you can write python, you can write tests in PyTest.

python assert - check that something is true

Test Discovery

Files named test*

Functions named test*

Demo Project

Trivial app as a demo

Print a summary of the latest HPR Episode

Title, Host, Date, Audio File

How do we get the latest show data

RSS feed

Feed parser

Feed URL

The pytest setup

The python script we want to test will be named

hpr_info.py

The test will be in a file will be named

test_hpr_info.py

test_hpr_info.py

import hpr_info

Run pytest

ModuleNotFoundError: No module named 'hpr_info'

We have written our first failing test.

The minimum code to get pytest to pass is to create an empty

file

touch hpr_info.py

Run pytest again

pytest

============================= test session starts ==============================

platform linux -- Python 3.11.8, pytest-7.4.4, pluggy-1.4.0

rootdir: /tmp/Demo

collected 0 items

What just happened

We created a file named test_hpr_info.py with a single

line to import hpr_info

We ran pytest and it failed because hpr_info.py did not exist

We created hpr_info.py and pytest ran without an

error.

This means we confirmed:

Pytest found the file named test_hpr_info.py and tried

to execute its tests

The import line is looking for a file named

hpr_info.py

Python Assert

In python, assert tests if a statement is true

For example

asert 1==1

In pytest, we can use assert to check a function returns a specific

value

assert module.function() == "Desired Output"

Without doing a comparison operator, we can also use assert to check

if something exists without specifying a specific value

assert dictionary.key

Adding a Test

Import hpr_info will allow us to test functions inside

hpr_info.py

We can reference functions inside hpr_info.py by

prepending the name with hpr_info. for example

hpr_info.HPR_FEED

The first step in finding the latest HPR episode is fetching a copy

of the feed.

Lets add a test to make sure the HPR feed is defined

import hpr_info

def test_hpr_feed_url():

assert hpr_info.HPR_FEED == "https://hackerpublicradio.org/hpr_ogg_rss.php"

pytest again

Lets run pytest again and we get the error

AttributeError: module 'hpr_info' has no attribute 'HPR_FEED'

So lets add the just enough code hpr_info.py to get the

test to pass

HPR_FEED = "https://hackerpublicradio.