Testing in Django

Why and how you should test in Django

Code without tests is broken as designed

 Jacob Kaplan-Moss

The Pinax Example

http://code.pinax.com/tasks Problem: Anyone with account could edit ticket status. 

The Pinax Example

Example of why this needed to be changed: • User adds ticket to a release already under feature

freeze. • User moves it to resolved.

 • Core developers have to remember every ticket.

 

The Pinax Example

Easy fix: • Django already supports groups and permissions 

 • add a new permission method to the state_transition

tuple 

The Pinax Example

Works!• Looks fine in my browser!

 • Looks fine in James Tauber's browser!

Flashback

Pycon 2009

• Daniel Mizyrycki, pythonista and hang glider enthusiast

 • Nixes the ability for anonymous users to add/modify

tasks • Writes two tests to confirm his change works

ERROR - Test Fail!

 

The Pinax Example

Daniel's tests toss out an error!

• Anonymous users break • is_task_manager method doesn't allow for task

viewing by anonymous users • Fix is easy:

   

Code without tests is broken as designed

 Jacob Kaplan-Moss

What about...

Selenium...Windchill...Nose...Twill...Your test system of choice...

All good stuff but outside the scope of this presentation.

Doctest or Unittest?

My pros and cons of Doctest

Pros • Easy to learn

 • Documents your code

 • Is pretty with RST

Cons • Kinda hard to maintain

 • Weirdness on

assertions

My pattern for Django unit tests

• Via Django Admin, add some sample data • In tasks application, mkdir fixtures

 • Via command line:

  

 ./manage.py dumpdata tasks >

apps/tasks/fixtures/test_tasks.json 

My pattern for Django unit tests

1.mkdir 'tests' folder in tasks2.touch test_authentication.py in tasks/tests 3.touch __init__.py folder in tasks/tests4.edit __init__.py to include:

     from test_authentication.py import *

My pattern for Django unit tests

The test setup:

My pattern for Django unit tests

The test:

My pattern for Django unit tests

Run the test!

    python manage.py test tasks

A bigger test

See how each method I write tests a different thing. Seems like a good pattern right now.

But you always find your old tests look silly.

You get better at writing tests the more you do it.

Things I like about tests

• Avoidance of embarrassment • Looks good

 • The rush

Questions? Comments?