Declarative Cucumber

Neat ways to use our favourite behavior driven development tool

About Me

Mario Visic

Developer at Sentia Australia

@mariovisic on Twitter

Why Use Cucumber?

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

Using

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

The 3 stages I went through

Using web steps (Imperative)
Using web steps as well as defining your own steps (Imperative)
Writing Declarative steps

Using web steps (Imperative)


# features/user/authentication.feature
Feature: Authentication (web steps)
  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"

# features/support/paths.rb
module NavigationHelpers
  def path_to(page_name)
    # ...

    when /^the member(s?) sign in page$/
      new_member_session_path

    # ...
  end
end

Problems with web steps

It doesn't read well in English
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 might actually be easier to learn than cucumber

Using web steps as well as defining your own steps (Imperative)


# features/user/authentication.feature
Feature: Authentication (web steps + Own)
  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

When /^I fill in my user details$/ do
  Then %{I fill in "Email" with "#{@current_email}"}
  Then %{I fill in "Password" with "#{@current_password}"}
end

Problems with keeping web steps

Reusing steps in other steps looks ugly and can get messy
Steps are easier to read but still do not match a story we would define for a feature
Scenarios are still written in imperative style (More on this in a second)

Writing Declarative steps (Without any web steps)

But firstly, what is Imperative and Declarative?

Imperative means that you write each step that needs to be taken to complete the outcome, for example "fill in the email form input".

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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