the “terrain”¶
Terrain is a “pun” with lettuce and its “living place”, its about setup and teardown, and general hacking on your lettuce tests.
terrain.py¶
By convention lettuce tries do load a file called terrain.py located at the current directory.
Think at this file as a global setup place, there you can setup global hooks, and put things into lettuce “world”.
Note
You can also set a terrain.py file within the root of your Django project, when running the python manage.py harvest command, lettuce will load it. See more at the django command.
in practice¶
Try out this file layout:
/home/user/projects/some-project
| features
- the-name-of-my-test.feature
- the-file-which-holds-step-definitions.py
- terrain.py
Then add some setup at terrain.py and run lettuce
user@machine:~/projects/some-project$ lettuce
And notice terrain.py will be loaded before anything
world¶
For the sake of turning easier and funnier to write tests, lettuce “violates” some principles of good design in python, such as avoiding implicity and using global stuff.
The “world” concept of lettuce is mostly about “global stuff”.
in practice¶
Imagine a file located somewhere that will be imported by your application before lettuce start running tests:
from lettuce import world
world.some_variable = "yay!"
So that, within some step file you could use things previously set on world:
from lettuce import *
@step(r'exemplify "world" by seeing that some variable contains "(.*)"')
def exemplify_world(step, value):
assert world.some_variable == value
And the feature could have something like:
Feature: test lettuce's world
Scenario: check variable
When I exemplify "world" by seeing that some variable contains "yay!"
world.absorb¶
It can be really useful to put functions and/or classes in lettuce.world
For example:
from lettuce import world
def my_project_wide_function():
# do something
world.my_project_wide_function = my_project_wide_function
world.my_project_wide_function()
But as you can notice, as your project grows, there can be a lot of repetitive lines, not DRY at all :(
In order to avoid that, lettuce provides a “absorb” decorator that lives within “world”
Let’s see it in action:
from lettuce import world
@world.absorb
def my_project_wide_function():
# do something
world.my_project_wide_function()
You can also use it with classes:
from lettuce import world
@world.absorb
class MyClass:
pass
assert isinstance(world.MyClass(), MyClass)
And even with lambdas, but in this case you need to name it
from lettuce import world
world.absorb(lambda: "yeah", "optimist_function")
assert world.optimist_function() == 'yeah'
world.spew¶
Well, if you read the topic above, you may be guessing: “if I keep stashing things in lettuce.world, it may bloat it sometime, or confuse member names along my steps, or hooks.
For those cases after “absorbing” something, world can also “spew” it.
from lettuce import world
@world.absorb
def generic_function():
# do something
assert hasattr(world, 'generic_function')
world.spew('generic_function')
assert not hasattr(world, 'generic_function')
hooks¶
Lettuce has hooks that are called sequentially before and after each action
Presented as python decorators, it can be used to take any actions you find useful.
For example, you can set a browser driver at world, and close the connection after all, populate database with test mass or anything you want, for example
Let’s see it from outside in
@before.all¶
This hook is ran before lettuce look for and load feature files
The decorated function takes NO parameters
from lettuce import *
@before.all
def say_hello():
print "Hello there!"
print "Lettuce will start to run tests right now..."
@after.all¶
This hook is ran after lettuce run all features, scenarios and steps
The decorated function takes a TotalResult as parameter, so that you can use the result statistics somehow
from lettuce import *
@after.all
def say_goodbye(total):
print "Congratulations, %d of %d scenarios passed!" % (
total.scenarios_ran,
total.scenarios_passed
)
print "Goodbye!"
@before.each_feature¶
This hook is ran before lettuce run each feature
The decorated function takes a Feature as parameter, so that you can use it to fetch scenarios and steps inside.
from lettuce import *
@before.each_feature
def setup_some_feature(feature):
print "Running the feature %r, at file %s" % (
feature.name,
feature.described_at.file
)
@after.each_feature¶
This hooks behaves in the same way @before.each_feature does, except by the fact that its ran after lettuce run the feature.
from lettuce import *
@after.each_feature
def teardown_some_feature(feature):
print "The feature %r just has just ran" % feature.name
@before.each_scenario¶
This hook is ran before lettuce run each scenario
The decorated function takes a Scenario as parameter, so that you can use it to fetch steps inside.
from lettuce import *
from fixtures import populate_test_database
@before.each_scenario
def setup_some_scenario(scenario):
populate_test_database()
@after.each_scenario¶
This hooks behaves in the same way @before.each_scenario does, except by the fact that its ran after lettuce run the scenario.
from lettuce import *
from database import models
@after.each_scenario
def teardown_some_scenario(scenario):
models.reset_all_data()
@before.each_step¶
This hook is ran before lettuce run each step
The decorated function takes a Step as parameter, so that you can use it to fetch tables and so.
from lettuce import *
@before.each_step
def setup_some_step(step):
print "running step %r, defined at %s" % (
step.sentence,
step.defined_at.file
)
@after.each_step¶
This hooks behaves in the same way @before.each_step does, except by the fact that its ran after lettuce run the step.
from lettuce import *
@after.each_step
def teardown_some_step(step):
if not step.hashes:
print "no tables in the step"
django-specific hooks¶
Since lettuce officially supports Django, there are a few specific hooks that help on setting up your test suite on it.
@before.harvest¶
This hook is ran before lettuce start harvesting your Django tests. It can be very useful for setting up browser drivers (such as selenium), before all tests start to run on Django.
The decorated function takes a dict with the local variables within the harvest management command.
from lettuce import *
from lettuce.django import django_url
from selenium import selenium
@before.harvest
def prepare_browser_driver(variables):
if variables.get('run_server', False) is True:
world.browser = selenium('localhost', 4444, '*firefox', django_url('/'))
world.browser.start()
@after.harvest¶
This hook is ran right after lettuce finish harvesting your Django tests. It can be very useful for shutting down previously started browser drivers (see the example above).
The decorated function takes a list of TotalResult objects.
from lettuce import *
@after.harvest
def shutdown_browser_driver(results):
world.browser.stop()
@before.each_app¶
This hook is ran before lettuce run each Django app.
The decorated function takes the python module that corresponds to the current app.
from lettuce import *
@before.each_app
def populate_blog_database(app):
if app.__name__ == 'blog':
from blog.models import Post
Post.objects.create(title='Nice example', body='I like writting!')
@after.each_app¶
This hook is ran after lettuce run each Django app.
The decorated function takes two arguments:
- the python module that corresponds to the current app.
- a TotalResult as parameter, so that you can use the result statistics somehow
from lettuce import *
@after.each_app
def clear_blog_database_if_successful(app, result):
if app.__name__ == 'blog':
if result.scenarios_ran is result.scenarios_passed:
from blog.models import Post, Comment
Comment.objects.all()
Post.objects.all()
@before.runserver and @after.runserver¶
These hooks are ran right before, and after lettuce starts up the built-in http server.
The decorated function takes a lettuce.django.server.ThreadedServer object.
from lettuce import *
from django.core.servers.basehttp import WSGIServer
@before.runserver
def prepare_database(server):
assert isinstance(server, WSGIServer)
import mydatabase
mydatabase.prepare()
@after.runserver
def say_goodbye(server):
assert isinstance(server, WSGIServer)
print "goodbye, see you soon"
@before.handle_request and @after.handle_request¶
These hooks are ran right before, and after lettuce’s built-in HTTP server responds to a request.
Both decorated functions takes these two arguments:
- a django.core.servers.basehttp.WSGIServer object.
- a lettuce.django.server.ThreadedServer object.
from lettuce import *
from django.core.servers.basehttp import WSGIServer
@before.handle_request
def print_request(httpd, server):
socket_object, (client_address, size) = httpd.get_request()
print socket_object.dup().recv(size)
@after.handle_request
def say_goodbye(httpd, server):
socket_object, (client_address, size) = httpd.get_request()
print "I've just finished to respond to the client %s" % client_address
Warning
all the handle_request hooks are run within a python thread. If something went wrong within a calback, lettuce can get stuck.