How to load data from a file, for a unit test, in python?

Question

I've written a specialized HTML parser, that I want to unit test with a couple of sample webpages I've downloaded.

In Java, I've used class resources, to load data into unit tests, without having to rely on them being at a particular path on the file system. Is there a way to do this in Python?

I found the doctest.testfile() function, but that appears to be specific to doctests. I'd like to just get a file handle, to a particular HTML file, which is relative to the current module.

Thanks in advance for any suggestions!

score 87 · Accepted Answer · edited Sep 22 '16 at 09:13

87

To load data from a file in a unittest, if the testdata is on the same dir as unittests, one solution :

TESTDATA_FILENAME = os.path.join(os.path.dirname(__file__), 'testdata.html')


class MyTest(unittest.TestCase)

   def setUp(self):
       self.testdata = open(TESTDATA_FILENAME).read()

   def test_something(self):
       ....

edited Sep 22 '16 at 09:13

Anto

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answered Nov 08 '11 at 11:36

Ferran

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Using the 'new' python [pathlib](https://docs.python.org/3.8/library/pathlib.html#module-pathlib) this command becomes: `TEST_FILE = pathlib.Path(__file__).parent.joinpath("testdata.html")` and then `TEST_FILE.open()`. Remember to `import pathlib` and please note the suggestion in the answer from @LeilaHC to properly close the testfile again, e.g. in the tearDown method. – Kim May 06 '20 at 15:32
[`pkg_resources`](https://setuptools.readthedocs.io/en/latest/pkg_resources.html) is a tool that comes with `setuptools`. If a package is installed, even with just `pip install -e` or `./setup.py develop`, then `pkg_resources` can find resource files just by knowing `__name__`. – kojiro Nov 07 '20 at 01:46

score 24 · Answer 2 · answered Jan 30 '19 at 15:43

24

This is based on Ferran's answer, but it closes the file during MyTest.tearDown() to avoid 'ResourceWarning: unclosed file':

TESTDATA_FILENAME = os.path.join(os.path.dirname(__file__), 'testdata.html')


class MyTest(unittest.TestCase)

   def setUp(self):
       self.testfile = open(TESTDATA_FILENAME)
       self.testdata = self.testfile.read()

   def tearDown(self):
       self.testfile.close()

   def test_something(self):
       ....

answered Jan 30 '19 at 15:43

Leila Hadj-Chikh

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For visibility, it might be better to edit Ferran's answer with your addition. – Splendor Feb 07 '19 at 23:59

score 2 · Answer 3 · answered Nov 08 '11 at 10:26

2

You can also use a StringIO or cStringIO to simulate a string containing your file's contents as a file.

answered Nov 08 '11 at 10:26

Christian Alis

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Ya, I thought of that, but it would require that I put all the HTML into a python file as a string, which I don't like as it's > 3k lines long – cberner Nov 09 '11 at 00:20

score 1 · Answer 4 · edited May 23 '17 at 12:02

1

I guess your task boils down to what's given here to get the current file. Then extend that path by the path to you HTML file and open it.

edited May 23 '17 at 12:02

Community

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answered Nov 08 '11 at 09:50

Johannes Charra

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How to load data from a file, for a unit test, in python?

4 Answers4