sample.rb

RSpec.describe SomeHelper do
  let(:helper_class) do
    Class.new do
      attr_reader :request
      
      include SomeHelper
      
      def initialize(request)
        @request = request
      end
    end
  end
  let(:request) { double("request", GET: { "blah" => "blah" }) }
  subject { helper_class.new(request) }
end