Rails Active Record cancel (save or create) within before_create callback without raising an exception

Question

Actually, I want to check the model callback.

system_details.rb (model)

class SystemDetail < ActiveRecord::Base
  belongs_to :user
  attr_accessible :user_agent

  before_create :prevent_if_same    

  def agent
    Browser.new(ua: user_agent, accept_language: 'en-us')
  end

  def prevent_if_same
    rec = user.system_details.order('updated_at desc').first
    return true unless rec
    if rec.user_agent == user_agent
      rec.touch
      return false
    end
  end
end

prevent_if_samethe method works fine and works as expected, but it throws an exception ActiveRecord::RecordNotSavedwhen it returns false and the exception breaks rspec test. I want it to silently cancel the save without raising an exception.

system_detail_spec.rb (rspec)

require 'rails_helper'

RSpec.describe SystemDetail, :type => :model do      

  context '#agent' do
    it 'Checks browser instance' do
      expect(SystemDetail.new.agent).to be_an_instance_of(Browser)
    end
  end

  context '#callback' do    
    it 'Ensure not creating consecutive duplicate records' do
      user = create :end_user
      system_detail = create :system_detail, :similar_agent, user_id: user.id
      updated_at  = system_detail.updated_at
      system_detail2 = create :system_detail, :similar_agent, user_id: user.id
      system_detail.reload

      expect(system_detail2.id).to be_nil
      expect(system_detail.updated_at).to be > updated_at
    end
  end        
end

The 2nd test #callbackfailed due to an exception.

Failures:

1) SystemDetail callback # ensures no duplicate entries Error / Error: system_detail2 = create: system_detail ,: similar_agent, user_id: user.id ActiveRecord :: RecordNotSaved: ActiveRecord :: RecordNotSaved

?

Answer 1

, validate :prevent_if_same, . . ,