instances_counter__module_spec.rb

require 'spec_helper'

module Counter
  def initialize
    @@instances_counter += 1
  end

  def self.instances_count
    @@instances_counter
  end

  def self.reset_counter
    @@instances_counter = 0
  end
end

class Car
  include Counter
end

class Truck
  include Counter
end

class Van
  include Counter
end

describe 'Instance counter' do
  before { Counter.reset_counter }

  it 'works with 2 cars' do
    Car.new
    Car.new

    expect(Counter.instances_count).to eq(2)
  end

  it 'works with car, van and truck' do
    Car.new
    Van.new
    Truck.new

    expect(Counter.instances_count).to eq(3)
  end

  it 'works with 2 cars, 4 vans and 3 trucks' do
    2.times { Car.new }
    4.times { Van.new }
    3.times { Truck.new }

    expect(Counter.instances_count).to eq(9)
  end
end