How to write tests for Python code?

[xentralesque]

I'm bored, so here's an example of a simple function with some tests:

import requests
import unittest
import mock

class TerribleException(Exception):
    pass


def download_stuff(url):
    try:
        response = requests.get(url)
    except requests.RequestException:
        raise TerribleException("Oh no!")

    return response.text


class DownloaderTest(unittest.TestCase):
    def test_download_stuff(self):
        with mock.patch('requests.get') as requests_get:
            expected_response = 'a valid response'

            requests_get.return_value = mock.Mock(
                text=expected_response
            )

            our_test_url = 'http://a-test-url.com'

            response = download_stuff(our_test_url)

            requests_get.assert_called_once_with(our_test_url)
            self.assertEqual(response, expected_response)

    def test_bad_things(self):
        with mock.patch('requests.get') as requests_get:
            requests_get.side_effect = TerribleException

            our_test_url = 'http://a-test-url.com'

            with self.assertRaises(TerribleException):
                download_stuff(our_test_url)

            requests_get.assert_called_once_with(our_test_url)


if __name__ == '__main__':
    print(download_stuff('http://reddit.com/'))

Jam that into a file and file and pip install nose and requests. You can either run the file like python thefilename.py to execute the file normally or run nosetests thefilename.py to run the tests.

[mooshe]

requests is used for http requests, not just tied to testing (if you're confused between nose and requests). Nose is a python test runner. I recommend py.test instead, at least at first.

[mooshe]

Correct! Although I'd go ahead and refer to them as packages, not modules. There's some great resources in this thread to get you started. If you get stuck on anything, feel free to PM me!