Declarative Cucumber

Neat ways to use our favourite behavior driven development tool

by @mariovisic

Behavior Driven Development? (BDD)

1) Failing acceptance test (Given I am a Visitor; Then I can view the homepage)
2) Create a Failing unit test and make it pass
3) Repeat steps 2 a few times
3) Passing acceptance test

Why you shouldn't cucumber

Another DSL to learn
Capyabara + RSpec (insert other tool) is good enough
No one to read or write the steps (No tickets? Cards? Really?)
The cucumber steps have to be written differently to what the stakeholders give us! <== Can fix this

Why Use Cucumber?

Promotes Behavior Driven Development (BDD)
Encourages minimal implementations
Written in a language stake holders can read and write
Side effects may include accidental integration testing

Installing Cucumber

Cucumber

# In your Gemfile:
gem 'cucumber-rails' # For rails projects
gem 'cucumber'       # Otherwise

# Install the the cucumber gem
bundle install

# Install cucumber in your rails app 
# (cucumber-rails only)
rails g cucumber:install

# Setup the test database
rake db:test:prepare

# To run the test suite
cucumber

"Cucumber is hard, let's make it easier!"

Learning all this is hard, a new DSL, BDD, all these steps
web_steps.rb were added to make it easier
But they just made everyone write their features badly
Now no longer generated (old projects might still have it)

Remove web steps

Examples

Starting with what you should avoid doing

Imperative

Imperative means that you write each step that needs to be taken to complete the outcome, for example:
"Fill in the email form input"
"Press the button submit button"


# features/user/authentication.feature
Feature: Authentication (Imperative)
  As A User
  In order to gain access to skynet
  I want to be able to login and logout

  Background:
    Given the following user exists:
      | email   | password |
      | z@b.com | giraffes |


# features/user/authentication.feature
Scenario: Logging in
  Given I am on the login page
  When I fill in "Email" with "z@b.com"
  And I fill in "Password" with "giraffes"
  And I press "Sign in"
  Then I should see "Signed in"

Problems with imperative steps

It doesn't read well in English (too long)
It's hard to use it for BDD (Need to know how all of the UI works beforehand)
Clients couldn't write scenarios without a developers help
If we can't read it then why not just use capybara directly? It's going to be much easier than learning cucumber

Surely we can reduce some of these steps?

Also why is the users email and password important? Surely I shouldn't have to write that?


# features/user/authentication.feature
Feature: Authentication (Imperative with Shortcuts)
  As A User
  In order to gain access to skynet
  I want to be able to login and logout

  Scenario: Logging in
    Given I have a valid account
    And I am on the login page
    When I fill in my user details
    And I press "Sign in"
    Then I should see "Signed in"

# features/step_definitions/authentication.rb
Given /^I have a valid account$/ do
  @current_email = 'my@email.com'
  @current_password = 'candles'
  @current_user = FactoryGirl.create(:user,
    :email => @current_email,
    :password => @current_password)
end

# Please do not do this. More on this later.
When /^I fill in my user details$/ do
  step %{I fill in "Email" with "#{@current_email}"}
  step %{I fill in "Password" with "#{@current_password}"}
end

Problems with keeping imperative style

Steps are easier to read but still do not match a story we would define for a feature

Delclarative Steps

Declarative means that you write the outcome for the scenario, which is how we write our user stories and how a client thinks of the parts of their project.

An example would be "Given a user has an account, they should be able to login"

The individual steps are not as important.

# features/user/authentication.feature
Feature: Authentication (No Web Steps, Declarative)
  As A User
  In order to gain access to skynet
  I want to be able to login and logout

  Scenario: Logging in
    Given I have a valid account
    Then I should be able to login

# features/step_definitions/authentication.rb
Then /^I should be able to login$/ do
  visit new_user_session_path
  fill_in_my_details
  click_button 'Sign in'
  page.should have_content 'Signed in'
end

Where do we put the `fill_in_my_details` method?

# features/support/helpers/authentication_helper.rb
module AuthenticationHelper
  def fill_in_my_details
    fill_in 'Email', :with => @current_email
    fill_in 'Password', :with => @current_password
  end
end

World(AuthenticationHelper)

Why is Declarative better?

It's easy for clients and developers to read
Scenarios can match actual user stories
Feature files only need altering if the user stories change.

These slides are online at: http://mariovisic.github.com/declarative_cucumber/

All code snippets are working examples from:
https://github.com/mariovisic/declarative_cucumber

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