Test driven development (TDD) is a concept of software development in which a new feature is developed by writing tests first, making it fail, and writing the code to make the test pass. This process continues iteratively until all the tests pass.
Starting to code with TDD enables developers to think about the test cases first rather than diving immediately in writing the code for the feature. In this case, the requirements and the scenarios are thought about in advance. In this blog, I will go through installing rspec and adding doing TDD. Rspec is used for writing automated tests.
First of all, I will start with rspec-rails.
1) Add following to the Gemfile:
group :test do
gem 'rspec-rails'
end
2) bundle install
3) rails generate rspec:install
This will create certain files like spec_helper.rb in spec/. This file contains the configuration for the test. For instance, the database cleaner for cleaning test database is added in spec_helper. For more details, please refer here.
Let us assume that, we have a model Post and it has attributes title and description. Add a file post_spec.rb:
spec/models/post_spec.rb
require "spec_helper"
describe "Post", :type => model do
it "has attributes name and author" do
post = Post.new(title: "New Post", description: "This is a new post")
post.save
expect(post.attributes).to include("title")
expect(post.attributes).to include("description")
expect(Post.count).to be(1)
expect(Post.first.title).to be("New Post")
expect(Post.first.description).to be("This is a new post")
end
end
When you run the rspec test with command
bundle exec rspec
There will be an error:
Uninitialized constant Post
Then you create a model with
rails g model Post
Then when you run the test again it will give an error saying:
Undefined method title for Class
So add a new migration to add attributes title and description to the model Post with
rails generate migration CreatePosts title:string description:text
This will create a migration file in db/migrations/xxxxxxxxxxxxxx_create_posts.rb (xxxxxxxxxxxxxx is the timestamp the migration is created). When you open this file, it will look like:
class CreatePosts < ActiveRecord::Migration
def change
create_table :posts do |t|
t.string :title
t.text :description
t.timestamps
end
end
end
Then run the migration with:
bundle exec rake db:create
(for the first time)
and:
bundle exec rake db:migrate
Then, getting back to the test again. Now when you run rspec again, the tests again fail and it says as you will have to define the attributes in model as well.
Add the following lines in your app/models/post.rb
attr_accessible :title, :description
Now, when you run the test again with bundle exec rspec
, your tests successfully pass. Congratulations, you just did TDD with rspec.
