bogus_spec.rb

require 'bogus/rspec'

class Model
  def initialize(argument)
  end

  def self.from_argument(argument)
    self.new(argument)
  end
end

class Service
  attr_reader :model_factory

  def initialize(model_factory)
    @model_factory = model_factory
  end

  def run(argument)
    model_factory.from_argument(argument)
  end
end

describe Service do
  fake(:model_class, as: :class) { Model }

  let(:argument) { :dummy }
  let(:service)  { described_class.new(model_class) }

  before  { service.run(argument) }

  specify { model_class.should have_received.from_argument(argument) }
  specify { model_class.should have_received.new(argument) }
end