cache_spec.rb

require 'rspec'

class CachedRepository
  def initialize(repository)
    @repository = repository
    @cache = {}
  end

  def find(id)
    unless @cache.include?(id)
      @cache[id] = @repository.find(id)
    end
    @cache[id]
  end
end


describe CachedRepository do
  it 'calls find only once' do
    repository = double
    expect(repository).to receive(:find).once

    cr = CachedRepository.new(repository)
    cr.find(5)
    cr.find(5)
  end

  it 'returns same value when called twice' do
    repository = double(find: :value)

    cr = CachedRepository.new(repository)
    expect(cr.find(5)).to eq(:value)
    expect(cr.find(5)).to eq(:value)
  end

  it 'returns different value when called with different args' do
    repository = double
    expect(repository).to receive(:find).with(5).and_return(:value)
    expect(repository).to receive(:find).with(6).and_return(:another_value)

    cr = CachedRepository.new(repository)
    expect(cr.find(5)).to eq(:value)
    expect(cr.find(6)).to eq(:another_value)
  end
end