Python Testing with pytest. Simple, Rapid, Effective, and Scalable. 2nd Edition

Test applications, packages, and libraries large and small with pytest, Python’s most powerful testing framework. Pytest helps you write tests quickly and keep them readable and maintainable. In this fully revised edition, explore pytest’s superpowers—simple asserts, fixtures, parametrization, markers, and plugins—while creating simple tests and test suites against a small database application. Using a robust yet simple fixture model, it’s just as easy to write small tests with pytest as it is to scale up to complex functional testing. This book shows you how.Pytest is undeniably the best choice for testing Python projects. It’s a full-featured, flexible, and extensible testing framework. Pytest’s fixture model allows you to share test data and setup procedures across multiple layers of tests. The pytest framework gives you powerful features such as assert rewriting, parametrization, markers, plugins, parallel test execution, and clear test failure reporting—with no boilerplate code.With simple step-by-step instructions and sample code, this book gets you up to speed quickly on this easy-to-learn yet powerful tool. Write short, maintainable tests that elegantly express what you’re testing. Speed up test times by distributing tests across multiple processors and running tests in parallel. Use Python’s built-in assert statements instead of awkward assert helper functions to make your tests more readable. Move setup code out of tests and into fixtures to separate setup failures from test failures. Test error conditions and corner cases with expected exception testing, and use one test to run many test cases with parameterized testing. Extend pytest with plugins, connect it to continuous integration systems, and use it in tandem with tox, mock, coverage, and even existing unittest tests.Write simple, maintainable tests quickly with pytest.Why a Second Edition?Both Python and pytest have changed since the first edition of this book was published in 2017. There have been updates to pytest that are now reflected in the book:New builtin fixturesNew flagsThe addition of package scope fixturesThere have also been updates to Python that are reflected in the book:The adoption of f-strings and pathlibThe addition of dataclassesAlso, since publication of the first edition, I have taught many, many people about pytest, and I think I’ve learned how to be a better teacher. The second edition not only expands on what is covered in the first edition—it grew from 7 to 16 chapters!—but also it presents the material in what I think is a more gradual, digestible manner.