Using Lettuce and WebTest to Test Your WSGI App

Maybe I’m weird, but I don’t use Django. At my office, we’re using a home brew framework. One thing that is missing from our framework is good testing. I came from a Rails background and one thing I missed was Cucumber. Thankfully, someone was nice enough to make a clone in Python. It’s called Lettuce and you can find out more here.

What I noticed about the Lettuce documentation, being as extensive as it is, there really is no info on how to use it with any other web framework than Django. I was a little discouraged at first, especially when I tried to use the Django’s test client standalone. That wasn’t pretty and I thought all was lost. Persistence led me to Ian Bicking’s WebTest. It’s a fairly simple library to do web testing. For instance: go to this URL, click on this button, and I should see “X”.

With Lettuce and WebTest in hand, I knew it would be feasible to use the two together. I just had to figure out how.

Writing the features is easy. The hard part was getting to use WebTest so I can interact with my WSGI app just like a browser would:

from lettuce import *
from webtest import TestApp

def set_browser():
    world.browser = TestApp(myapp)

@step(u'Given I am a visitor')
def given_i_am_a_visitor(step):

@step(u'When I access the url "(.*)"')
def access_url(step, url):
    world.response = world.browser.get(url)

@step(u'Then I should see "(.*)"')
def i_should_see(step, text):
    text in world.response

It’s simple, really. The only trickery was to use the @before.all decorator to set the world browser as WebTest’s TestApp. From that point on, I can use WebTest like normal.

Hope this helps someone out there!