agent.rb

class Agent < ActiveRecord::Base
  validates :first_name, :last_name, :email, presence: true
  validates :email, uniqueness: true
  has_many :missions
  scope :on_assignment, -> { Agent.joins(:missions).where(missions: { status: 'active' }) }
  scope :not_on_assignment, -> { where.not(id: Agent.on_assignment.pluck(:id)) }

  def name
    "#{first_name} #{last_name}"
  end

  def on_assignment?
    missions.active.any?
  end

  def contract_end_date
    created_at.to_date + 5.years
  end

  def days_active
    Date.today - created_at.to_date
  end
end

agent_test.rb

require 'test_helper'

class AgentTest < ActiveSupport::TestCase
  test 'has valid test data' do
    assert_valid agents(:bond)
  end

  test 'must have an email first_name and last_name' do
    invalid_agent = Agent.new
    assert_invalid invalid_agent
    assert_includes invalid_agent.errors[:email], "can't be blank"
    assert_includes invalid_agent.errors[:first_name], "can't be blank"
    assert_includes invalid_agent.errors[:last_name], "can't be blank"
  end

  test 'must have a unique email' do
    copy_cat = Agent.new(email: agents(:bond).email)
    assert_invalid copy_cat
    assert_includes copy_cat.errors[:email], 'has already been taken'
  end

  test 'on_assignment collects agents on active missions' do
    agents_on_assigment = Agent.on_assignment
    assert_includes agents_on_assigment, agents(:bond)
    refute_includes agents_on_assigment, agents(:bourne)
  end

  test 'not_on_assignment collects agents not on active missions' do
    agents_not_on_assigment = Agent.not_on_assignment
    assert_includes agents_not_on_assigment, agents(:bourne)
    refute_includes agents_not_on_assigment, agents(:bond)
  end

  test 'name combines the first and last name' do
    assert_equal 'James Bond', agents(:bond).name
  end

  test 'on_assignment? should be true if an agent is on an active mission' do
    assert agents(:bond).on_assignment?, ':bond should be on an active mission'
  end

  test 'on_assignment? should be false if an agent is not on an active mission' do
    refute agents(:bourne).on_assignment?, ':bourne should not be on an active mission'
  end

  test 'contract_end_date should be 5 years after creation date' do
    assert_equal 5.years.from_now.to_date, agents(:bond).contract_end_date
  end

  test 'days_active returns the number of days since created_at' do
    agents(:bond).created_at -= 20.days
    assert_equal 20, agents(:bond).days_active
  end
end

agents.yml

bond:
  first_name: James
  last_name: Bond
  email: [email protected]

mendez:
  first_name: Tony
  last_name: Mendez
  email: [email protected]

bourne:
  first_name: Jason
  last_name: Bourne
  email: [email protected]

missions.yml

thunderball:
  code_name: Operation Thunderball
  description: Recover the atomic bombs stolen by SPECTRE.
  status: active
  agent: bond

argo:
  code_name: Argo
  description: Extract hostages in hiding from Iran.
  status: completed
  agent: mendez

test_helper.rb

ENV["RAILS_ENV"] ||= "test"
require File.expand_path('../../config/environment', __FILE__)
require 'rails/test_help'

class ActiveSupport::TestCase
  ActiveRecord::Migration.check_pending!
  fixtures :all

  # Add more helper methods to be used by all tests here...
  def assert_valid(record, message = nil)
    message ||= "Expected #{record.inspect} to be valid"
    assert record.valid?, message
  end

  def assert_invalid(record, options = {})
    assert record.invalid?, "Expected #{record.inspect} to be invalid"
    options.each do |attribute, message|
      assert_includes record.errors[attribute], message
    end
  end
end