pytest-tmpfs

A pytest plugin that helps you on using a temporary filesystem for testing

import json

def readjson(path: str) -> dict:
  """
  Example:
    >>> path = fs.write('a/b/c.json', '{"a": 2}')
    >>> readjson(path)
    {'a': 2}
  """
  with open(path, 'r') as f:
    return json.load(f)

This plugin is a fake filesystem manager implementation that relies on the pytest's tmp_path fixture to enable safe testing of projects that require disk operations and are difficult to mock.

Alternatives

• pyfakefs: good alternative if you wish to mock filesystem operations.
• tempfile: creates files and directories temporarily.

Install

For installing this package, just type the command below in your terminal:

pip install pytest-tmpfs

Usage

As a fixture

You can use the TmpFs as a fixture by passing tmpfs as an argument of your test function.

import pytest_tmpfs

def test_readjson(tmpfs: pytest_tmpfs.TmpFs):
    path = tmpfs.write('a/b/d.json', '{"a": 2}')
    assert readjson(path) == {'a': 2}

In doctests

By installing this plugin, all doctests are automatically enabled to use fs, a variable that stores an instance of TmpFs.

def fscheck(path: str) -> dict:
  """
  Example:
    >>> fs.touch('a/b/c.txt')
    >>> fs.ls('a/b')
    ['c.txt']
  """
  pass

Your own instance

If you seek to use this plugin without pointing to tmp_path it is possible to create your own instance and to manipulate it the way you want.

import pytest_tmpfs

def test_random():
  mypath = pathlib.Path('a/b/c')
  fs = TmpFs(mypath)

Features

The following table contains all methods that TmpFs implements and its descriptions:

Method	Description	Example	Parameters	Return
write	writes a file in the disk and adds line by line content to it	fs.write('a/b.txt', 'Hello', 'World!')	path, *lines	abs path to the file
read	reads the contents of a file and returns it as a string	fs.read('a/b.txt')	path	abs path to the file
ls	lists all files inside a folder	fs.ls('a')	path	sorted list of folders and files
rm	removes a file or a folder	fs.rm('a')	path	True if succeded, False if not
mkdir	creates one or more folders	fs.mkdir('b/c')	path	abs path to the folder
mv	moves a file or a folder to another path	fs.mv('a/b.txt', 'b/c')	path, path	abs path to destination
clean	removes all files inside the root of the tmp fs	fs.clean()
path	converts a relative path into an abs path	fs.path('a')	path	abs path to the file or folder
tree	prints a tree-like structure of a folder	fs.tree('a')	path
tree_format	same as tree, but outputs a string	fs.tree_format('a')	path	tree representation
cat	prints the content of a file	fs.cat('b/c/b.txt')	path
touch	creates an empty file	fs.touch('a/c.txt')	path	abs path to the file
tmp_cwd	changes CWD to the temporary filesystem folder	fs.tmp_cwd()		abs path to the fs root
cwd	returns to the original CWD	fs.cwd()		abs path to the old cwd

Note: tmp_cwd and cwd can be used with with statements.

Contributing

Feel free to contribute to this project, just remember to use pre-commit and to write unit tests for new features/bugs.