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Questions tagged [pyfakefs]

pyfakefs implements a fake file system that mocks the Python file system modules. If using pyfakefs, the tests operate on a fake file system in memory without touching the real disk. pyfakefs directly supports unittest and pytest, and can be used with other testing frameworks.

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How to replace file-access references for a module under test

pyfakefs sounds very useful: it "was developed initially as a modest fake implementation of core Python modules to support moderately complex file system interactions, and was introduced Google-wide . . . in September 2006. Since then, it has…
intuited
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Mocking disk-out-of-space in python unittests

I'm trying to write a unittest to test the behaviour of a function when the disk is full. I need file access functions to behave normally while most of the test runs, so that the file I'm creating is actually created, then at one point I need the…
askvictor
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Programmatically execute a Python file from within Python in a fresh-looking Python environment

Let's say I have a file script.py located at path = "foo/bar/script.py". I'm looking for a way in Python to programmatically execute script.py from within my main Python program through a function execute_script(). However, I've got a few…
balu
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importlib_resources backport not compatible with pyfakefs?

I'm refactoring a library to use importlib.resources for python 3.7+. I'm using the importlib_resources backport for python 3.6 compatibility. The code works for pythons 3.6-3.8. However, the pytest tests, using pyfakefs, fail for 3.6. Under testing…
Geoffrey Sametz
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Is it possible to mock the platform for reading and writing files in binary and text mode?

I would to test if a system reads and writes files correctly (text mode / binary mode) on multiple platforms, at least on linux and windows. (Using pytest). See https://docs.python.org/2/tutorial/inputoutput.html#reading-and-writing-files It is…
sunew
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Pyfakefs not supporting os.renames?

Here's a simple piece of code I wanted to test: import os def move_all(firstPath, secondPath): for count, filename in enumerate(os.listdir(firstPath)): print('moving '+str(count) + ' '+filename) …
Honkou
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Why FileNotFoundError on Path.rename while using Pyfakefs?

I wrote a test for a function that renames files from e.g. /videos/vid_youtube.mp4 to /videos/youtube/vid.mp4. The test patches the fs with Pyfakefs. When the code actually renames the file, I get this error. FileNotFoundError: [Errno 2] No such…
progonkpa
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Patching over local JSON file in unit testing

I have some Python code that loads in a local JSON file: with open("/path/to/file.json") as f: json_str = f.read() # Now do stuff with this JSON string In testing, I want to patch that JSON file to be a JSON file located in my repo's test…
Intrastellar Explorer
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Keep pathlib.(Posix)Path patched by pyfakefs when subclassing it

I have subclassed PosixPath this way: from pathlib import PosixPath class Node(PosixPath): def __new__(cls, *args, mykwarg=None, **kwargs): self = super().__new__(cls, *args, **kwargs) self._mykwarg = mykwarg return…
zezollo
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Mocking class methods, still running the original method with some wrapped code

I want to patch a method by running the original method with additional code before and after. In particular, I'm running tests within a pyfakefs in-memory file system, but I want to sometime use the real file system because some packages will not…
kdauria
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How to use pyfakefs in conjunction with importlib.resources.path

Given some installed package, the following code can be used to print its location on the filesystem: import importlib.resources def print_package_path(pkg): with importlib.resources.path(pkg, "") as path: …
Arne
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How to test aiofiles with pyfakefs in a synchronous test class

Consider the function in a module. async def _get_user_mapping(): async with aiofiles.open('/etc/subuid') as f: async for line in f: print(line) And a test class from atestfile import _get_user_mapping class…
TechnicalChaos
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Real file system accessed when running lxml with pyfakefs

How can I run lxml with pyfakefs? import os import unittest from lxml import etree from pyfakefs import fake_filesystem_unittest class TestExample(fake_filesystem_unittest.TestCase): def setUp(self): self.setUpPyfakefs() def…
Oskar Persson
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pyfakefs breaks tests using requests

I have a Pytest test using the pyfakefs fs fixture. def test_my_unit_test(fs): simple_test() It works as expected and simple tests run with the fake filesystem provided by pyfakefs. If I run another test that uses requests, I get this error…
Nicolas Berthier
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Pytestfs write then read doesn't return expected value

I'm trying to write a test involving the filesystem. I chose to use pyfakefs and pytest for writing these tests. When I was trying to write and then read from the fake filesystem, I couldn't seem to get any tests to work. So, I wrote a simple test…
Julia Norman
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