_python

Example

To start things off let's pull in our requisite libraries (import unittest for our test framework, from selenium import webdriver to drive the browser, and import httplib for our HTTP library), declare our test class, and wire up some test setUp and tearDown methods.

# filename: file_download_revisited.py
import unittest
from selenium import webdriver
import httplib # Use http.client if using Python 3.x.x
from selenium.webdriver.common.by import By


class FileDownloadRevisited(unittest.TestCase):

    def setUp(self):
        self.driver = webdriver.Firefox()

    def tearDown(self):
        self.driver.quit()
# ...

Now we're ready to write up our test.

It's just a simple matter of visiting the page with download links, grabbing a URL from one of them, and performing a HEAD request with it.

# filename: file_download_revisited.py
# ...
    def test_example_1(self):
        driver = self.driver
        driver.get('http://the-internet.herokuapp.com/download')
        download_link = driver.find_element(By.CSS_SELECTOR,'.example a').get_attribute('href')

        connection = http.client.HTTPConnection('the-internet.herokuapp.com')
        connection.request('HEAD', download_link)
        response = connection.getresponse()
        content_type = response.getheader('Content-type')
        content_length = response.getheader('Content-length')
        content_length = int(content_length)

        assert content_type == 'application/octet-stream'
        assert content_length > 0

if __name__ == "__main__":
    unittest.main()

Once we receive the response we can check its header for the Content-type and Content-length to make sure the file is the correct type and not empty.

Expected Behavior

When you save this and run it (e.g., python file_download_revisited.py from the command-line) here is what will happen:

• Open the browser
• Load the page
• Grab the URL of the first download link
• Perform a HEAD request against it with an HTTP library
• Store the response
• Check the response headers to see that the file type is correct
• Check the response headers to see that the file is not empty

Summary

Compared to the browser specific configuration with Selenium this is hands down a leaner, faster, and more maintainable approach. But unfortunately it only works with files served up from a flat URL. So if you're trying to test file downloads that are generated in-memory as part of the browser session (a.k.a. not accessible from a URL) then you'll need to reach for the browser specific Selenium configuration.

Happy Testing!