cocktail_spec.rb

# Rspec test (with FactoryGirl) for Stackoverflow question https://stackoverflow.com/questions/46728121 

describe 'with_ingredients' do
  subject { Cocktail.with_ingredients(ingredient_ids) }

  context 'one cocktail, one ingredient, zero cocktail ingredient' do
    let(:cocktail) { create :cocktail }
    let(:ingredient) { create :ingredient }
    let(:ingredient_ids) { [ingredient.id] }

    before { create :cocktail_ingredient, cocktail: cocktail }

    it { is_expected.to eq [] }
  end

  context 'one cocktail, one ingredient' do
    let(:cocktail) { create :cocktail }
    let(:ingredient) { create :ingredient }
    let(:ingredient_ids) { [ingredient.id] }

    before { create :cocktail_ingredient, cocktail: cocktail, ingredient: ingredient }

    it { is_expected.to eq [cocktail] }
  end

  context 'three cocktails, two ingredients' do
    let(:cocktail) { create :cocktail }
    let(:cocktail2) { create :cocktail }
    let(:cocktail3) { create :cocktail }
    let(:ingredient) { create :ingredient }
    let(:ingredient2) { create :ingredient }
    let(:ingredient_ids) { [ingredient.id, ingredient2.id] }

    before do
      create :ingredient
      create :cocktail_ingredient
      create :cocktail_ingredient, cocktail: cocktail, ingredient: ingredient
      create :cocktail_ingredient, cocktail: cocktail2, ingredient: ingredient
      create :cocktail_ingredient, cocktail: cocktail, ingredient: ingredient2
      create :cocktail_ingredient, cocktail: cocktail3, ingredient: ingredient2
    end

    it { is_expected.to eq [cocktail] }
  end
end