Working with BDD

The concept of Behaviour Driven Development (BDD) is pretty simple. You describe what you want the system to do by describing potential users interactions with the different parts of the application. You work outside-in to implement features using the examples to validate that you're building the right thing at the right time. During this workshop you will see BDD in action and will experience, at least partially, the benefits of this method.

The tools we will be using to test our application are RSpec and Cucumber. Those are the two so called testing frameworks that will help us to write good code. During the development process, we'll take an approach that combines high level acceptance tests and low level unit tests to both drive the development process and make sure that we build a robust and well structured application.

Test first

Let's start with writing some high level acceptance tests.

What we want to do at this stage is to get the user stories we have defined and look at them from a user's perspective. Also, what an actual implementation of features would look like. In short, we want to take each user story and break it down to scenarios that each represents a use case in the application. Sounds confusing? It is, but look at it as a form of a blue print that you will use when we start to actually build the app.

Cucumber (cucumber.io) is a testing framework used to describe high level functionality of your application. We will refer to them as acceptance test or features. One of Cucumber's most compelling features is that, it allows you to write these descriptions in plain text. Even in your native language.

Cucumber is not installed on your system so we need to do that as a first step.

Open your terminal and let's setup the project folder:

$ mkdir workshop
$ cd workshop
$ echo "source 'https://rubygems.org'" > Gemfile
$ echo "gem 'cucumber'" >> Gemfile

Now run the following command..

$ bundle install

..and watch the system install it together with some other libraries it depends on in order to be able to run,

Once that is complete I'd like you to initiate Cucumber by simply typing in:

$ cucumber --init

That will create some files and folders for you:

create   features
create   features/step_definitions
create   features/support
create   features/support/env.rb

Okay, now, in your terminal, you type in:

$ cucumber

The output you will see should look something like this:

0 scenarios
0 steps
0m0.000s

Alright, we have installed and initiated the first testing framework. Big step.

Now let's take a moment to talk about how a Cucumber file is built and then we'll write our first of many tests.

A feature is defined by one or more scenarios. A scenario is a sequence of steps through the feature that exercises one path.

A scenario is made up of 3 sections related to the 3 types of steps:

• Given: This sets up preconditions, or context, for the scenario.

• When: This is what the feature is talking about, the action, the behavior that we're focused on.

• Then: This checks postconditions. It verifies that the right thing happen in the When stage.

There is yet another type of step you can use in a scenario path, and that is the And keyword. And can be used in any of the three sections. It serves as a nice shorthand for repeating the Given, When, or Then. And stands in for whatever the most recent explicitly named step was.

In the newly created features folder, please create a course_create.feature by returning to your terminal window and typing in:

$ touch features/course_create.feature

Open that file and add the following code:

Feature: As a course administrator,
  In order to be able to issue certificates,
  I want to be able to create a course offering with a description and multiple delivery dates

The Feature: description is added mainly for your and your fellow project members reference. It tells a reader what this test file is actually about - setting the scope for the scenarios.

As the next step, we will add two basic scenarios:

# features/course_create.feature

Scenario: List courses
  Given I am on the home page
  And I am logged in as an administrator
  When I click "All courses" link
  Then I should see "You have not created any courses"

Scenario: Create a course
  Given I am on the home page
  And I am logged in as an administrator
  And I click "All courses" link
  And I click "Create course" link
  And I fill in "Course Title" with "Basic programming"
  And I fill in "Course description" with "Your first step into the world of programming"
  And I click "Create" link
  Then a new "Course" should be created
  And I should be on the Course index page
  And I should see "Basic programming"

Let's have a look at the first one:

1. The 2 preconditions for our scenario is that we have logged in to the application and are currently visiting the root path of the app.

2. The action I'm taking is clicking on the All courses link.

3. The postcondition is the fact that I see the message "You have not created any courses"

Now in your terminal window, go ahead and type cucumber again and watch the test framework do its job. If you have followed my instructions, you will see an output similar to this:

$ cucumber
Feature: As a course administrator,
  In order to be able to issue certificates,
  I want to be able to create a course offering with a description and multiple delivery dates

  Scenario: List courses                                 # features/course_create.feature:5
    Given I am on the home page                          # features/course_create.feature:6
    And I am logged in as an administrator               # features/course_create.feature:7
    And I click "All courses" link                       # features/course_create.feature:8
    Then I should see "You have not created any courses" # features/course_create.feature:9

  Scenario: Create a course                                                          # features/course_create.feature:11
    Given I am on the home page                                                      # features/course_create.feature:12
    And I am logged in as an administrator                                           # features/course_create.feature:13
    And I click "All courses" link                                                   # features/course_create.feature:14
    And I click 'Create course" link                                                 # features/course_create.feature:15
    And I fill in "Title" with "Basic programming"                                   # features/course_create.feature:16
    And I fill in "Description" with "Your first step into the world of programming" # features/course_create.feature:17
    And I click "Create" link                                                        # features/course_create.feature:18
    Then a new "Course" should be created                                            # features/course_create.feature:19
    And I should be on the Course index page                                         # features/course_create.feature:20
    And I should see "Basic programming"                                             # features/course_create.feature:21

2 scenarios (2 undefined)
14 steps (14 undefined)
0m0.237s

And also:

You can implement step definitions for undefined steps with these snippets:

Given(/^I am on the home page$/) do
  pending # Write code here that turns the phrase above into concrete actions
end

Given(/^I am logged in as an administrator$/) do
  pending # Write code here that turns the phrase above into concrete actions
end

Given(/^I click "([^"]*)" link$/) do |arg1|
  pending # Write code here that turns the phrase above into concrete actions
end

Then(/^I should see "([^"]*)"$/) do |arg1|
  pending # Write code here that turns the phrase above into concrete actions
end

Given(/^I fill in "([^"]*)" with "([^"]*)"$/) do |arg1, arg2|
  pending # Write code here that turns the phrase above into concrete actions
end

Then(/^a new "([^"]*)" should be created$/) do |arg1|
  pending # Write code here that turns the phrase above into concrete actions
end

Then(/^I should be on the Course index page$/) do
  pending # Write code here that turns the phrase above into concrete actions
end

This is perfectly normal, and means that we need to start doing some serious programming in order to actually implement the tests and eventually make them pass.