handler_spec.rb

require 'active_support/all'

class Rails
  def self.logger=(logger)
    @logger = logger
  end

  def self.logger
    @logger
  end
end

class Car
  class Wheel
    def initialize(message)
    end

    def perform
    end
  end
end

class Handler
  def self.receive(model, action, message)
    begin
      "#{model.classify}::#{action.classify}".constantize.new(message).perform
    rescue NameError
      Rails.logger.info("No map for #{model.classify}::#{action.classify}")
      return
    end
  end
end


describe Handler do
  let(:log) { StringIO.new }

  before do
    Rails.logger = Logger.new(log)
  end

  it "should log missing classes" do
    Handler.receive("User", "Action", "testing")
    log.rewind
    logged_messages = log.read

    expect(logged_messages).to include("No map for User::Action")
  end

  it "should not log present classes" do
    value = Handler.receive("Car", "Wheel", "testing")
    log.rewind
    logged_messages = log.read

    expect(logged_messages).not_to include("No map for Car::Wheel")
  end
end

~/tmp❯ rspec handler_spec.rb
..

Finished in 0.0021 seconds (files took 0.75384 seconds to load)
2 examples, 0 failures
~/tmp❯