Relationships

Associations:

See: Active Record Associations
Types:

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1. Install the shoulda-matchers gem:
This will help me test associations without writing a lo lot of code (since I'm working with test-driven development). Remember to run bundle. 

2. I'll add todo-items to our to-do list (I could've done a scaffold, but I'm going to do it manually). I'll also use model instead of scaffold because we're going to do something called "nesting" the todo-items inside of our todo-list and resource declaration.

Generate the todo-item model:

bin/rails generate model todo_item todo_list:references content:string

Run: rake db:migrate

Migrate my test database as well:
rake db:migrate RAILS_ENV=test

> models >todo_item.spec
require 'spec_helper'

describe TodoItem do
  it {should belong_to (:todo_list)}
end

>models >todo_list.spec
require 'spec_helper'

describe TodoList do
  it {should have_many(:todo_items)}
end

todo_list.rb
has_many :todo_items