Saturday, 22 November 2008

TempDirTestCase, a Python unittest helper

I have seen a lot of unittest-based test cases written in Python that create temporary directories in setUp() and delete them in tearDown().

Creating temporary directories is such a common thing to do that I have a base class that provides a make_temp_dir() helper method. As a result, you often don't have to define setUp() and tearDown() in your test cases at all.

I have ended up copying this into different codebases because it's easier than making the codebases depend on an external library for such a trivial piece of code. This seems to be quite common: lots of Python projects provide their own test runners based on unittest.

Here's the code:

import shutil
import tempfile
import unittest

class TempDirTestCase(unittest.TestCase):

    def setUp(self):
        self._on_teardown = []

    def make_temp_dir(self):
        temp_dir = tempfile.mkdtemp(prefix="tmp-%s-" % self.__class__.__name__)
        def tear_down():
        return temp_dir

    def tearDown(self):
        for func in reversed(self._on_teardown):

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