deck.rb

class Deck
  attr_accessor :size

  def size
    cards.size
  end

  def cards
    cards = []
    52.times { cards << 1 }
    cards
  end
end
# binding.pry

deck_spec.rb

require 'rspec'
require 'pry'

require_relative 'deck'

RSpec.describe do
  it 'has 52 cards' do
    expect(Deck.new.size).to eq(52)
  end

  it 'has 52 cards' do
    expect(Deck.new.cards.first).to be_kind_of Integer
  end
end