person_specs.rb

RSpec.describe Person do
  let(:person) { described_class.new('Fixed', 'Name', education_level, educator) }

  describe '#educate' do
    let(:education_level) { 2 }
    let(:educator) { instance_double('PersonEducator') }
    let(:updated_education_level) { education_level + 1 }
    
    subject { person.education_level }

    before do
      expect(educator).to receive(:educate).and_return(updated_education_level)
      person.educate
    end

    it { is_expected.to eq updated_education_level }
  end
end