OOP Review, RSpec Review and Modules

cat.rb

require_relative 'jsonable'

require 'pry-byebug'

class Party
  def self.throw_party(number_of_candles)
    'We are partying'
    true
  end
end

class Cat
  include JSONable
  attr_reader :name, :age, :happy

  def initialize(*args)
    @name = args[0]
    @age = age[1]
  end

  def speak
    'meow'
  end

  def celebrate_birthday
    @age += 1
    @happy = Party.throw_party(@age)
  end
end

cat_spec.rb

require_relative "../lib/cat"


RSpec.describe Cat do
  let(:name) { 'Bob' }
  let(:age) { 3 }

  subject { Cat.new(name, age) }

  # This tests a query method
  describe '#name' do
    it 'returns the name of the cat' do
      expect(subject.name).to eq name
    end
  end

  # This tests a command/query function
  describe '#speak' do
    it 'speaks like a cat' do
      expect(subject.speak).to eq 'meow'
    end
  end

  # This tests a query method
  describe '#age' do
    it 'returns the age of the cat' do
      expect(subject.age).to eq age
    end
  end

  # This tests a command function
  describe '#celebrate_birthday' do
    let(:throw_party_result) { true }

    before do
      allow(Party).to receive(:throw_party)
                       .and_return(throw_party_result)
      subject.celebrate_birthday
    end

    it 'adds a year to the age of the cat' do
      expect(subject.age).to eq age + 1
    end

    # this test an external object using a Mock
    it 'throws a party' do
      expect(Party).to have_received(:throw_party)
                        .with(age + 1)
    end

    it 'the cat is happy' do
      expect(subject.happy).to be_truthy
    end

    # Another mock test
    context 'when the party go wrong' do
      let(:throw_party_result) { false }

      it 'then my cat will be sad' do
        expect(subject.happy).to be_falsey
      end
    end
  end
end

jsonable.rb

require 'json'

module JSONable

  def self.included(base)
    base.extend ClassMethods
  end

  module ClassMethods
    def create_from_json(json_string)
      obj = new
      object = JSON.parse(json_string)
      object.each do |key, value|
        next if key == 'class_name'
        obj.instance_variable_set key, value
      end
      obj
    end
  end

  def to_json(*a)
    result = {}
    result[:class_name] = self.class.name
    self.instance_variables.each do |key|
      result[key] = self.instance_variable_get key
    end
    result.to_json(*a)
  end
end

modules.rb

module MyModule
  # this is a constant
  PI = 3.14
  
  # This is a module function. Good for utility functions
  def self.foo
    'foo'
  end
  
  # This class is namespaced
  class Foo
    ...
  end
end