Oliveira - Pytest quick start guide : write better Python code with simple and maintainable tests

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pytest is one of the projects that show off the best qualities of Python; it is the easiest Python testing framework to get started and also the most powerful. The pytest developers leverage metaprogramming to help users; we can write tests as plain functions and use the
assert keyword for checks, which means we can use any Python expression as a check, and we don't need to memorize the names of dozens of assertThis, assertThat methods. When there is a test failure, pytest uses sophisticated introspection to show the difference between the expected value and the value returned by the code under test. Introspection and decorators are also used to provide fixtures, parameters, grouping, skipping, and such like.

pytest is basically two parts: a library that gives you the API to write tests, and a test runner, a command-line utility that can search and execute tests across your project packages. The behavior of the pytest CLI can be configured in many ways, as described in this guide. By default, pytest is smart enough to collect tests written with the standard unittest package as well as doctest, running them and reporting all their results together. This means you can start using pytest now to run the tests you've already written with unittest and doctest.

pytest is very powerful out of the box, but it can also be enhanced by a large collection of industrial-strength plugins. A good collection of the best plugins is covered in this book.

If you are in the business of writing libraries and APIs for others to use, pytest is not only a great tool, but also a plentiful source of ideas and techniques, leveraging the best features of Python.

Anyone willing to learn pytest will be lucky to be guided by Bruno Oliveira, a long-time core developer of this most practical, powerful, and Pythonic package.

Thank you for your work on pytest, Bruno and for writing this book.

Valeu!

Luciano Ramalho
Principal consultant at Thoughtworks and author of Fluent Python

Bruno Oliveira is a software developer with 18 years experience working at ESSS, developing desktop and web applications for simulation and numerical analysis for several industry sectors including oil and gas, aerospace, automotive, and chemical processes. Having taken part in the development of an internal testing framework to attend to the various needs of the applications he worked with, and having always been interested in testing and software quality, in 2012, Bruno took note of pytest and immediately fell in love with the project. He started contributing whenever he could and has been a pytest core contributor since 2014.

Igor T. Ghisi is a software developer with a BSc in computer science and an MSc in computational mechanics. He has worked for 10 years in the largest research center in Latin America, in Rio de Janeiro, building software for R&D in engineering using agile practices, with a focus on the oil and gas industry. He developed software for 3D Mesh Generation, Mesh Visualization, Reservoir Simulation, Uncertainty, and Multi-disciplinary Optimization . He switched to web development over the last four years to solve engineering problems using web and cloud technologies.

Edson Tadeu Monteiro Manoel has more than 15 years' experience working in scientific software development, mostly using a mix of C++ and Python. He has been using pytest in his everyday work since 2013.

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Automated tests are a very important tool in a developer's tool belt. Having a set of automated tests not only increases productivity and software quality; it also works as a safety net for developers and gives confidence in relation to code refactorings. Python comes with a standard unittest module that is used to write automated tests, but there's an alternative: pytest. The pytest framework is simple to get started with, and scales from simple unit tests all the way through to complex integration testing. It is considered by many to be truly Pythonic in its approach, with simple functions, plain asserts, fixtures, plugins, and a whole plethora of features. More and more developers are adopting a full testing approach, so why not use a framework that is both simple and powerful and considered by many to be a true joy to use?