1# pyfakefs [](https://badge.fury.io/py/pyfakefs) [](https://img.shields.io/pypi/pyversions/pyfakefs.svg)  2 3pyfakefs implements a fake file system that mocks the Python file system modules. 4Using pyfakefs, your tests operate on a fake file system in memory without 5touching the real disk. The software under test requires no modification to 6work with pyfakefs. 7 8pyfakefs works with Linux, Windows and MacOS. 9 10## Documentation 11 12This file provides general usage instructions for pyfakefs. There is more: 13 14* The documentation at [GitHub Pages:](http://jmcgeheeiv.github.io/pyfakefs) 15 * The [Release documentation](http://jmcgeheeiv.github.io/pyfakefs/release) 16 contains usage documentation for pyfakefs and a description of the 17 most relevant classes, methods and functions for the last version 18 released on PyPi 19 * The [Development documentation](http://jmcgeheeiv.github.io/pyfakefs/master) 20 contains the same documentation for the current master branch 21 * The [Release 3.7 documentation](http://jmcgeheeiv.github.io/pyfakefs/release37) 22 contains usage documentation for the last version of pyfakefs 23 supporting Python 2.7 24 * The [Release 3.3 documentation](http://jmcgeheeiv.github.io/pyfakefs/release33) 25 contains usage documentation for the last version of pyfakefs 26 supporting Python 2.6, and for the old-style API (which is still 27 supported but not documented in the current release) 28* The [Release Notes](https://github.com/jmcgeheeiv/pyfakefs/blob/master/CHANGES.md) 29 show a list of changes in the latest versions 30 31### Linking to pyfakefs 32 33In your own documentation, please link to pyfakefs using the canonical URL <http://pyfakefs.org>. 34This URL always points to the most relevant top page for pyfakefs. 35 36## Usage 37 38pyfakefs has support for `unittest` and `pytest`, but can also be used 39directly using `fake_filesystem_unittest.Patcher`. Refer to the 40[usage documentation](http://jmcgeheeiv.github.io/pyfakefs/master/usage.html) 41for more information on test scenarios, test customization and 42using convenience functions. 43 44 45## Compatibility 46pyfakefs works with CPython 3.6 and above, on Linux, Windows and OSX 47(MacOS), and with PyPy3. 48 49pyfakefs works with [pytest](http://doc.pytest.org) version 3.0.0 or above. 50 51pyfakefs will not work with Python libraries that use C libraries to access the 52file system. This is because pyfakefs cannot patch the underlying C libraries' 53file access functions--the C libraries will always access the real file system. 54For example, pyfakefs will not work with [`lxml`](http://lxml.de/). In this case 55`lxml` must be replaced with a pure Python alternative such as 56[`xml.etree.ElementTree`](https://docs.python.org/3/library/xml.etree.elementtree.html). 57 58## Development 59 60### Continuous integration 61 62pyfakefs is currently automatically tested on Linux, MacOS and Windows, with 63Python 3.6 to 3.10, and with PyPy3 on Linux, using 64[GitHub Actions](https://github.com/jmcgeheeiv/pyfakefs/actions). 65 66### Running pyfakefs unit tests 67 68#### On the command line 69pyfakefs unit tests can be run using `unittest` or `pytest`: 70 71```bash 72$ cd pyfakefs/ 73$ export PYTHONPATH=$PWD 74 75$ python -m pyfakefs.tests.all_tests 76$ python -m pyfakefs.tests.all_tests_without_extra_packages 77$ python -m pytest pyfakefs/pytest_tests/pytest_plugin_test.py 78``` 79 80These scripts are called by `tox` and Travis-CI. `tox` can be used to run tests 81locally against supported python versions: 82 83```bash 84$ tox 85``` 86 87#### In a Docker container 88 89The `Dockerfile` at the repository root will run the tests on the latest 90Ubuntu version. Build the container: 91```bash 92cd pyfakefs/ 93docker build -t pyfakefs . 94``` 95Run the unit tests in the container: 96```bash 97docker run -t pyfakefs 98``` 99 100### Contributing to pyfakefs 101 102We always welcome contributions to the library. Check out the 103[Contributing Guide](https://github.com/jmcgeheeiv/pyfakefs/blob/master/CONTRIBUTING.md) 104for more information. 105 106## History 107pyfakefs.py was initially developed at Google by Mike Bland as a modest fake 108implementation of core Python modules. It was introduced to all of Google 109in September 2006. Since then, it has been enhanced to extend its 110functionality and usefulness. At last count, pyfakefs is used in over 2,000 111Python tests at Google. 112 113Google released pyfakefs to the public in 2011 as Google Code project 114[pyfakefs](http://code.google.com/p/pyfakefs/): 115* Fork 116 [jmcgeheeiv-pyfakefs](http://code.google.com/p/jmcgeheeiv-pyfakefs/) added 117 [direct support for unittest and doctest](../../wiki/Automatically-find-and-patch-file-functions-and-modules) 118* Fork 119 [shiffdane-jmcgeheeiv-pyfakefs](http://code.google.com/p/shiffdane-jmcgeheeiv-pyfakefs/) 120 added further corrections 121 122After the [shutdown of Google Code](http://google-opensource.blogspot.com/2015/03/farewell-to-google-code.html) 123was announced, [John McGehee](https://github.com/jmcgeheeiv) merged all three Google Code projects together 124[here on GitHub](https://github.com/jmcgeheeiv/pyfakefs) where an enthusiastic community actively supports, maintains 125and extends pyfakefs. 126
){kind=link}
){kind=link}
){kind=link}