# Lettuce Behaviour Driven Development for python

# 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”.

### 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:

So that, within some step file you could use things previously set on `world`:

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:

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:

You can also use it with classes:

And even with lambdas, but in this case you need to name it

### 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.

## 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 :ref:lettuce-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

### @after.all

This hook is ran after lettuce run all features, scenarios and steps

The decorated function takes a :ref:total-result as parameter, so that you can use the result statistics somehow

### @before.each_feature

This hook is ran before lettuce run each feature

The decorated function takes a :ref:feature-class as parameter, so that you can use it to fetch scenarios and steps inside.

### @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.

### @before.each_scenario

This hook is ran before lettuce run each scenario

The decorated function takes a :ref:scenario-class as parameter, so that you can use it to fetch steps inside.

### @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.

### @before.each_step

This hook is ran before lettuce run each step

The decorated function takes a :ref:step-class as parameter, so that you can use it to fetch tables and so.

#### @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.

## 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.

### @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 :ref:total-result objects.

### @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.

### @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 :ref:total-result as parameter, so that you can use the result statistics somehow

### @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.

### @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.