blah_spec.rb

describe Blah do
  attr_reader :john, :mary

  before(:each) do
    @john = Webrat.session_class.new(self)
    @mary = Webrat.session_class.new(self)
  end

  it "does stuff concurrently" do
    mary.visit "/"
    john.visit "/"

    ...
  end
end