:game_die: Pytest plugin to randomly order tests and control random.seed

Related tags

Testingpytest
Overview

pytest-randomly

https://img.shields.io/github/workflow/status/pytest-dev/pytest-randomly/CI/main?style=for-the-badge https://img.shields.io/pypi/v/pytest-randomly.svg?style=for-the-badge https://img.shields.io/badge/code%20style-black-000000.svg?style=for-the-badge pre-commit
Randomness power.

Pytest plugin to randomly order tests and control random.seed.

Features

All of these features are on by default but can be disabled with flags.

  • Randomly shuffles the order of test items. This is done first at the level of modules, then at the level of test classes (if you have them), then at the order of functions. This also works with things like doctests.
  • Resets random.seed() at the start of every test case and test to a fixed number - this defaults to time.time() from the start of your test run, but you can pass in --randomly-seed to repeat a randomness-induced failure.
  • If factory boy is installed, its random state is reset at the start of every test. This allows for repeatable use of its random 'fuzzy' features.
  • If faker is installed, its random state is reset at the start of every test. This is also for repeatable fuzzy data in tests - factory boy uses faker for lots of data. This is also done if you're using the faker pytest fixture, by defining the faker_seed fixture (docs).
  • If numpy is installed, its random state is reset at the start of every test.
  • If additional random generators are used, they can be registered under the pytest_randomly.random_seeder entry point and will have their seed reset at the start of every test. Register a function that takes the current seed value.
  • Works with pytest-xdist.

About

Randomness in testing can be quite powerful to discover hidden flaws in the tests themselves, as well as giving a little more coverage to your system.

By randomly ordering the tests, the risk of surprising inter-test dependencies is reduced - a technique used in many places, for example Google's C++ test runner googletest. Research suggests that "dependent tests do exist in practice" and a random order of test executions can effectively detect such dependencies [1]. Alternatively, a reverse order of test executions, as provided by pytest-reverse, may find less dependent tests but can achieve a better benefit/cost ratio.

By resetting the random seed to a repeatable number for each test, tests can create data based on random numbers and yet remain repeatable, for example factory boy's fuzzy values. This is good for ensuring that tests specify the data they need and that the tested system is not affected by any data that is filled in randomly due to not being specified.

I have written a blog post covering the history of pytest-randomly, including how it started life as the nose plugin nose-randomly.

Additionally, I appeared on the Test and Code podcast to talk about pytest-randomly.

Installation

Install from pip with:

python -m pip install pytest-randomly

Python 3.6 to 3.9 supported.


Testing a Django project? Check out my book Speed Up Your Django Tests which covers loads of best practices so you can write faster, more accurate tests.


Usage

Pytest will automatically find the plugin and use it when you run pytest. The output will start with an extra line that tells you the random seed that is being used:

$ pytest
...
platform darwin -- Python 3.7.2, pytest-4.3.1, py-1.8.0, pluggy-0.9.0
Using --randomly-seed=1553614239
...

If the tests fail due to ordering or randomly created data, you can restart them with that seed using the flag as suggested:

pytest --randomly-seed=1234

Or more conveniently, use the special value last:

pytest --randomly-seed=last

Since the ordering is by module, then by class, you can debug inter-test pollution failures by narrowing down which tests are being run to find the bad interaction by rerunning just the module/class:

pytest --randomly-seed=1234 tests/module_that_failed/

You can disable behaviours you don't like with the following flags:

  • --randomly-dont-reset-seed - turn off the reset of random.seed() at the start of every test
  • --randomly-dont-reorganize - turn off the shuffling of the order of tests

The plugin appears to Pytest with the name 'randomly'. To disable it altogether, you can use the -p argument, for example:

pytest -p no:randomly

Entry Point

If you're using a different randomness generator in your third party package, you can register an entrypoint to be called every time pytest-randomly reseeds. Implement the entrypoint pytest_randomly.random_seeder, referring to a function/callable that takes one argument, the new seed (int).

For example in your setup.cfg:

[options.entry_points]
pytest_randomly.random_seeder =
    mypackage = mypackage.reseed

Then implement reseed(new_seed).

References

[1] Sai Zhang, Darioush Jalali, Jochen Wuttke, Kıvanç Muşlu, Wing Lam, Michael D. Ernst, and David Notkin. 2014. Empirically revisiting the test independence assumption. In Proceedings of the 2014 International Symposium on Software Testing and Analysis (ISSTA 2014). Association for Computing Machinery, New York, NY, USA, 385–396. doi:https://doi.org/10.1145/2610384.2610404
Owner
pytest-dev
pytest-dev
Avocado is a set of tools and libraries to help with automated testing.

Welcome to Avocado Avocado is a set of tools and libraries to help with automated testing. One can call it a test framework with benefits. Native test

Ana Guerrero Lopez 1 Nov 19, 2021
Sixpack is a language-agnostic a/b-testing framework

Sixpack Sixpack is a framework to enable A/B testing across multiple programming languages. It does this by exposing a simple API for client libraries

1.7k Dec 24, 2022
A automated browsing experience.

browser-automation This app is an automated browsing technique where one has to enter the required information, it's just like searching for Animals o

Ojas Barawal 3 Aug 04, 2021
Testing - Instrumenting Sanic framework with Opentelemetry

sanic-otel-splunk Testing - Instrumenting Sanic framework with Opentelemetry Test with python 3.8.10, sanic 20.12.2 Step to instrument pip install -r

Donler 1 Nov 26, 2021
API Test Automation with Requests and Pytest

api-testing-requests-pytest Install Make sure you have Python 3 installed on your machine. Then: 1.Install pipenv sudo apt-get install pipenv 2.Go to

Sulaiman Haque 2 Nov 21, 2021
Yet another python home automation project. Because a smart light is more than just on or off

Automate home Yet another home automation project because a smart light is more than just on or off. Overview When talking about home automation there

Maja Massarini 62 Oct 10, 2022
Testinfra test your infrastructures

Testinfra test your infrastructure Latest documentation: https://testinfra.readthedocs.io/en/latest About With Testinfra you can write unit tests in P

pytest-dev 2.1k Jan 07, 2023
Python tools for penetration testing

pyTools_PT python tools for penetration testing Please don't use these tool for illegal purposes. These tools is meant for penetration testing for leg

Gourab 1 Dec 01, 2021
Data-Driven Tests for Python Unittest

DDT (Data-Driven Tests) allows you to multiply one test case by running it with different test data, and make it appear as multiple test cases. Instal

424 Nov 28, 2022
Automated tests for OKAY websites in Python (Selenium) - user friendly version

Okay Selenium Testy Aplikace určená k testování produkčních webů společnosti OKAY s.r.o. Závislosti K běhu aplikace je potřeba mít v počítači nainstal

Viktor Bem 0 Oct 01, 2022
Python Moonlight (Machine Learning) Practice

PyML Python Moonlight (Machine Learning) Practice Contents Design Documentation Prerequisites Checklist Dev Setup Testing Run Prerequisites Python 3 P

Dockerian Seattle 2 Dec 25, 2022
PoC getting concret intel with chardet and charset-normalizer

aiohttp with charset-normalizer Context aiohttp.TCPConnector(limit=16) alpine linux nginx 1.21 python 3.9 aiohttp dev-master chardet 4.0.0 (aiohttp-ch

TAHRI Ahmed R. 2 Nov 30, 2022
HTTP load generator, ApacheBench (ab) replacement, formerly known as rakyll/boom

hey is a tiny program that sends some load to a web application. hey was originally called boom and was influenced from Tarek Ziade's tool at tarekzia

Jaana Dogan 14.9k Jan 07, 2023
Generic automation framework for acceptance testing and RPA

Robot Framework Introduction Installation Example Usage Documentation Support and contact Contributing License Introduction Robot Framework is a gener

Robot Framework 7.7k Jan 07, 2023
pytest plugin providing a function to check if pytest is running.

pytest-is-running pytest plugin providing a function to check if pytest is running. Installation Install with: python -m pip install pytest-is-running

Adam Johnson 21 Nov 01, 2022
This repository contnains sample problems with test cases using Cormen-Lib

Cormen Lib Sample Problems Description This repository contnains sample problems with test cases using Cormen-Lib. These problems were made for the pu

Cormen Lib 3 Jun 30, 2022
MongoDB panel for the Flask Debug Toolbar

Flask Debug Toolbar MongoDB Panel Info: An extension panel for Rob Hudson's Django Debug Toolbar that adds MongoDB debugging information Author: Harry

Cenk Altı 4 Dec 11, 2019
A simple python script that uses selenium(chrome web driver),pyautogui,time and schedule modules to enter google meets automatically

A simple python script that uses selenium(chrome web driver),pyautogui,time and schedule modules to enter google meets automatically

3 Feb 07, 2022
Just a small test with lists in cython

Test for lists in cython Algorithm create a list of 10^4 lists each with 10^4 floats values (namely: 0.1) - 2 nested for iterate each list and compute

Federico Simonetta 32 Jul 23, 2022