How can I store testing data for python nosetests?

Question

I want to write some tests for a python MFCC feature extractor for running with nosetest. As well as some lower-level tests, I would also like to be able to store some standard input and expected-output files with the unit tests.

At the moment we are hard-coding the paths to the files on our servers, but I would prefer the testing files (both input and expected-output) to be somewhere in the code repository so they can be kept under source control alongside the testing code.

The problem I am having is that I'm not sure where the best place to put the testing files would be, and how to know what that path is when nosetest calls each testing function. At the moment I am thinking of storing the testing data in the same folder as the tests and using __file__ to work out where that is (would that work?), but I am open to other suggestions.

Answer 1

Based on the idea of using __file__, maybe you could use a module to help with the path construction. You could find all the files contained in the module directory, gather their name and path in a dictionnary for later use.

Create a module accessible to your tests, i.e. a directory besides your test such as testData, where you can put your data files. In the __init__.py of this module, insert the following code.

import os
from os.path import join,dirname,abspath
testDataFiles = dict()
baseDir = dirname(abspath(__file__)) + os.path.sep 
for root, dirs, files in os.walk(baseDir):
    localDataFiles = [(join(root.replace(baseDir,""),name), join(root,name)) for name in files] 
    testDataFiles.update( dict(localDataFiles))

Assuming you called your module testData and it contains a file called data.txt you can then use the following construct in your test to obtain the path to the file. aFileOperation is assumed to be a function that take a parameter path

import unittest
from testData import testDataFiles

class ATestCase(unittest.TestCase):
    def test_Something(self):
        self.assertEqual( 0, aFileOperation(testDataFiles['data.txt'] )

It will also allow you to use subdirectories such as

    def test_SomethingInASubDir(self):
        self.assertEqual( 0, aFileOperation(testDataFiles['subdir\\data.txt'] )

Answer 2

I think that using __file__ to figure out where the test is located and storing data alongside the it is a good idea. I'm doing the same for some tests that I write.

This:

os.path.dirname(os.path.abspath(__file__))

is probably the best you are going to get, and that's not bad. :-)