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Automating your API tests using Python and Pytest

Alicia Marianne on November 12, 2023

Did you ever thought how you can tests your APIs using python? In the article we will learn how we can test our APIs using Python and the pytest fr...

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Prayson Wilfred Daniel • Nov 16 '23 • Edited

Really good step by step introduction to testing with pytest.

I usually Mock external calls with Postman as I wish not to respect the service, which I don’t own, with my tests.

from os import environ
import requests

def make_request():

    base_url = environ.get("BASE_URL")
    params = {"api_key": environ.get("API_KEY"),}
    response = requests.get(url=base_url, params=params)

    return response

Postman has a good section here on how to mock external API

We would then inject URL and keys from environment variables 😉 which enable us to change Mocked and Real in our CI/CD without changing our code.

So the actions that do unit tests, will have mocked values, and ones doing integration will have real.

Brent Brewington • Nov 13 '23 • Edited

Really nice post! Always good to explain virtual environments while working with Python, and I like the straightforward pytest example you provide

Best practice with unit testing code that calls API's is to mock the API interface, so you don't have to ping an external service (idea of unit tests is to be able to run them very quickly with very little external dependencies, if any). Here's a great RealPython article that walks through how to do this mocking...and just a heads up this might get a little more advanced for some readers, but good to know it's out there!

realpython.com/testing-third-party...

^ heads up, that example uses "nosetest" library (extension of unittest) rather than "pytest"

Here's a great explanation of when it makes sense to actually call the external API in tests: pytest-with-eric.com/pytest-best-p...

Christian Ledermann • Nov 13 '23

For mocking external API calls responses and HTTPretty are my favourite helpers

Alicia Marianne • Nov 13 '23

Thanks! This article was focused more on integration tests than unit tests, I'll take a look at your recommendations.

Christian Ledermann • Nov 13 '23

Have you heard of schemathesis, a tool that automates your API testing to catch crashes and spec violations? Built on top of the widely-used Hypothesis framework for property-based testing.

Also available as a service

Alicia Marianne • Nov 13 '23

Nice! I'll take a look at this one, I've never heard before.

Ganesh • Nov 17 '23

pytest test.py --html-report=./report/report.html

this should be

pytest test.py --html=./report/report.html

Ganesh • Nov 18 '23

Python 3.9.7
Platform Windows-10-10.0.19045-SP0
Packages pytest: 7.4.3
pluggy: 1.0.0
Plugins html: 4.1.1
metadata: 3.0.0

The above is my environment and the --html-report=./report.html did not work in this environment.

BTW, Sorry I forgot to mention that your tutorial was excellent. Even though I have been using python for past twenty years, I understood and started using pytest only after reading this. Thanks for the simple and lucid tutorial

Alicia Marianne • Nov 17 '23

How I used pytest-html-reporter library, the recommendation on the documentation is to run:

--html-report=./report/report.html

You can check here more about it:
github.com/prashanth-sams/pytest-h...

Naveen • Feb 5 • Edited

Somehow, I am getting errors if my response includes dates. For the time being, I am using --html=./report/report.html. I need to find an alternative way to see a good HTML report that can show results in a graphical manner.