How to debug failing tests in Django?

Question

How do I debug my tests? For example, I POST to create an entry and expect it to validate and return a particular page. It works in the browser and in the shell, but the test is the only thing that fails (ironically!). I would like to print the response to the console or something so I could read errors or what have you. But I can only see things that I print in e.g. the view.

Not sure it's necessary, but here's the test code in question from tests.py:

    resp = self.client.post('/meal/invite/',          {'summary': 'Test munch', 'when': now(), 'max_diners': '1', 'description': 'Munchies'}, follow=True)     self.assertEqual(resp.status_code, 200)     self.assertContains(resp, 'Test munch', 1)     self.assertContains(resp, 'You are hosting this meal', 1) 

The final assertion is incorrect. If I change it to a value present in the original form page showing 'field required' errors, it passes. I just can't see what I'm missing.

I have a few other tests working, but I just don't know how to debug this.

How is it done?

Answer 1

You can drop in a pdb and inspect everything.

If you're using nose i believe you have to run your tests with -s

 -s, --nocapture       Don't capture stdout (any stdout output will be                         printed immediately) [NOSE_NOCAPTURE] 

This is what keeps you from seeing output immediately.

Answer 2

To run the test under pdb:

python -m pdb manage.py test yourapp 

I agree with Alasdair, the print response.content (and printing stuff in general) is a great help. The output gets mixed up with the normal test runner output, and should be removed once you find the problem and fix it, but it can help you narrow down the problem.

Also, if the code works in the browser and the shell but not the unit test, remember that the unit test makes a new (empty) database. Ensure that your setUp puts in any data that is required for your test.

(Updated the code part from Patrick's suggestion, thanks Patrick)