require 'rails_helper'

RSpec.describe 'CustomSet' do
  let(:set) { CustomSet.new(init_data) }

  describe '#exist?' do
    subject { set.exist?(element) }

    context 'set already have data' do
      let(:init_data) { [1, 2] }

      context 'element exists in set' do
        let(:element) { 1 }

        it { is_expected.to eq true }
      end

      context 'element does not exist in set' do
        let(:element) { 3 }

        it { is_expected.to eq false }
      end
    end

    context 'set does not have data' do
      let(:init_data) { [] }
      let(:element) { 1 }

      it { is_expected.to eq false }
    end
  end

  describe '#add' do
    let(:init_data) { [1, 2] }

    after do
      expect(set.exist?(element)).to eq true
    end

    context 'added element exists in set' do
      let(:element) { 1 }

      it 'does not add to set' do
        expect { set.add(element) }.not_to change { set.data.length }
      end
    end

    context 'added element does not exists in set' do
      let(:element) { 3 }

      it 'adds element to set' do
        expect { set.add(element) }.to change { set.data.length }.by(1)
      end
    end
  end

  describe '#remove' do
    subject(:remove_element) { set.remove(element) }

    let(:init_data) { [1, 2] }

    after do
      expect(set.exist?(element)).to eq false
    end

    context 'removed element exists in set' do
      let(:element) { 1 }

      it 'removes element from set' do
        expect { remove_element }.to change { set.data.length }.by(-1)
        expect(remove_element).to eq element
      end
    end

    context 'removed element does not exists in set' do
      let(:element) { 3 }

      it 'does not remove element from set' do
        expect { set.remove(element) }.not_to change { set.data.length }
        expect(remove_element).to be_nil
      end
    end
  end
end