Package: pyfakefs
pyfakefspyfakefs implements a fake file system that mocks the Python file system modules.
Using pyfakefs, your tests operate on a fake file system in memory without
touching the real disk. The software under test requires no modification to
work with pyfakefs.Pyfakefs creates a new empty in-memory file system at each test start, which replaces
the real filesystem during the test. Think of pyfakefs as making a per-test temporary
directory, except for an entire file system.There are several means to achieve this: by using
thefsfixture if running pytest, by usingfake_filesystem_unittest.TestCaseas a
base class if using unittest, by using afake_filesystem_unittest.Patcherinstance
as a context manager, or by using thepatchfsdecorator.pyfakefs works with current versions of Linux, Windows and macOS.DocumentationThis document provides a general overview for pyfakefs.  There is more:The documentation atRead the Docs:TheRelease documentationcontains usage documentation for pyfakefs and a description of the
most relevant classes, methods and functions for the last version
released on PyPITheDevelopment documentationcontains the same documentation for the current main branchTheRelease 3.7 documentationcontains usage documentation for the last version of pyfakefs
supporting Python 2.7TheRelease Notesshow a list of changes in the latest versionsUsageThe simplest method to use pyfakefs is using thefsfixture withpytest.
Refer to theusage documentationfor information on other test scenarios, test customization and
using convenience functions.FeaturesApart from automatically mocking most file-system functions, pyfakefs
provides some additional features:mapping files and directories from the real file system into the fake filesystemconfiguration and tracking of the file system sizepause and resume of patching to be able to use the real file system inside a
test step(limited) emulation of other OSes (Linux, macOS or Windows)configuration to behave as if running as a non-root user while running
under rootCompatibilitypyfakefs works with CPython 3.7 and above, on Linux, Windows and macOS, and
with PyPy3.pyfakefs works withpytestversion 3.0.0 or above,
though a current version is recommended.pyfakefs will not work with Python libraries that use C libraries to access the
file system. This is because pyfakefs cannot patch the underlying C libraries'
file access functions--the C libraries will always access the real file
system. Refer to thedocumentationfor more information about the limitations of pyfakefs.DevelopmentContinuous integrationpyfakefs is currently automatically tested on Linux, macOS and Windows, with
Python 3.7 to 3.12, and with PyPy3 on Linux, usingGitHub Actions.Running pyfakefs unit testsOn the command linepyfakefs unit tests can be run usingpytest(all tests) orunittest(all tests exceptpytest-specific ones):$cdpyfakefs/
$exportPYTHONPATH=$PWD$python-mpytestpyfakefs
$python-mpyfakefs.tests.all_testsSimilar scripts are called bytoxand Github Actions.toxcan be used to
run tests locally against supported python versions:$toxIn a Docker containerTheDockerfileat the repository root will run the tests on the latest
Ubuntu version.  Build the container:cdpyfakefs/
dockerbuild-tpyfakefs.Run the unit tests in the container:dockerrun-tpyfakefsContributing to pyfakefsWe always welcome contributions to the library. Check out theContributing Guidefor more information.Historypyfakefs.py was initially developed at Google by Mike Bland as a modest fake
implementation of core Python modules.  It was introduced to all of Google
in September 2006. Since then, it has been enhanced to extend its
functionality and usefulness.  At last count, pyfakefs was used in over 2,000
Python tests at Google.Google released pyfakefs to the public in 2011 as Google Code projectpyfakefs:Forkjmcgeheeiv-pyfakefsaddeddirect support for unittest and doctestForkshiffdane-jmcgeheeiv-pyfakefsadded further correctionsAfter theshutdown of Google Codewas announced,John McGeheemerged all three Google Code projects togetherhere on GitHubwhere an enthusiastic community actively supports, maintains
and extends pyfakefs. In 2022, the repository has been transferred topytest-devto ensure continuous maintenance.