pytest: helps you write better programs

The pytest framework makes it easy to write small tests, yet scales to support complex functional testing for applications and libraries.

An example of a simple test:

# content of
def inc(x):
    return x + 1

def test_answer():
    assert inc(3) == 5

To execute it:

$ pytest
=========================== test session starts ============================
platform linux -- Python 3.x.y, pytest-4.x.y, py-1.x.y, pluggy-0.x.y
cachedir: $PYTHON_PREFIX/.pytest_cache
collected 1 item F                                                     [100%]

================================= FAILURES =================================
_______________________________ test_answer ________________________________

    def test_answer():
>       assert inc(3) == 5
E       assert 4 == 5
E        +  where 4 = inc(3) AssertionError
========================= 1 failed in 0.12 seconds =========================

Due to pytest’s detailed assertion introspection, only plain assert statements are used. See Getting Started for more examples.


  • Detailed info on failing assert statements (no need to remember self.assert* names);
  • Auto-discovery of test modules and functions;
  • Modular fixtures for managing small or parametrized long-lived test resources;
  • Can run unittest (including trial) and nose test suites out of the box;
  • Python 2.7, Python 3.4+, PyPy 2.3, Jython 2.5 (untested);
  • Rich plugin architecture, with over 315+ external plugins and thriving community;


Please see Contents for full documentation, including installation, tutorials and PDF documents.


Please use the GitHub issue tracker to submit bugs or request features.


Consult the Changelog page for fixes and enhancements of each version.


Copyright Holger Krekel and others, 2004-2020.

Distributed under the terms of the MIT license, pytest is free and open source software.