a_question.rb

class Something
  def happen(dependency)
    dependency.use
  end
end

class Dependency
  def initialize
    @used = false
  end

  def use
    @used = true
  end

  def used?
    @used
  end
end

describe Something do
  describe '#happen' do
    it 'depends' do
      dependency = Dependency.new
      something = Something.new

      something.happen(dependency)

      expect(dependency).to be_used
    end
  end
end