Railslove Ruby programming exercise A2

subsets.rb

# Railslove Ruby programming exercise A2
#
# To run the following exercise you need to have rspec installed.
# Then inspect the failing specs by running `rspec subset.rb`
#
# The task is to get all possible subsets of a group of Railslovers (without duplicates).
# So return a collection containing a group of each Railslover alone,
# then a group of pairs, then groups of 3, etc...
# The empty group is not considered a valid Railslove group. :)
#
# Write code in the body of the subsets method to make the tests pass.
#
# Refactor until you're happy with your solution, by asking the follwing questions:
#   * Is the code understandable/maintainable?
#   * Do I really need all these if/else/elsif statements?
#
require 'ostruct'

class Collection < OpenStruct
  def subsets
    #
    # your code goes here
    #
    railslovers
  end
end


# don't touch me
require 'rspec'
RSpec.describe 'Collection' do
  let(:railslovers) { %w(Bumi Jan Tim Lars) }

  subject(:collection) { Collection.new(railslovers: railslovers) }

  describe '#subsets' do
    it 'returns not the initial collection' do
      expect(subject.subsets).not_to eq(railslovers)
    end

    it 'is already a big collection for four railslovers' do
      expect(subject.subsets.size).to eq(15)
    end

    it 'contains groups of 1' do
      expect(subject.subsets).to include(['Bumi'])
      expect(subject.subsets).to include(['Jan'])
      expect(subject.subsets).to include(['Tim'])
      expect(subject.subsets).to include(['Lars'])
    end

    it 'contains groups of 2' do
      expect(subject.subsets).to include(['Bumi', 'Tim'])
      expect(subject.subsets).to include(['Bumi', 'Jan'])
      expect(subject.subsets).to include(['Jan', 'Tim'])
      expect(subject.subsets).to include(['Jan', 'Lars'])
    end

    it 'contains groups of 3' do
      expect(subject.subsets).to include(['Jan', 'Tim', 'Lars'])
      expect(subject.subsets).to include(['Bumi', 'Tim', 'Lars'])
    end

    it 'contains groups of 4' do
      expect(subject.subsets).to include(railslovers)
    end
  end
end