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A configurable demo mode for your Rails app. Specify your desired "personas" and DemoMode will handle the rest.
 Project Readme

Demo Mode

Gem Version Tests

DemoMode is a drop-in "demo" interface for Rails apps, replacing your app's sign-in form with a very customizable "persona" picker, with a list of personas that can be defined in just a few lines of code. Each persona represents a kind of user template, allowing you to generate fresh accounts over and over.

This gem can be used to produce custom deployments of your app, and is ideal for enabling πŸ’ͺ highly reliable and repeatable product demos πŸ’ͺ. It can also be used to produce sandbox deployments of your app/APIs, and since it also ships with a developer CLI, it is a super convenient tool for local development (as a replacement for pre-generated user seeds).

All icons, names, logos, and styles can be customized with your own branding, but if all you do is define a few personas, you'll get a fully-functioning interface out of the box (with your app's name in the upper left):

We recommend pairing this gem with webvalve (to isolate your app from any collaborating HTTP services) as well as a "factory" DSL like factory_bot (for generating accounts concisely). That said, you'll get the most mileage out of whatever tools you already use in local development & testing, so if you already have solutions for isolating your app and generating users, use those!

To learn more about how we use demo_mode at Betterment, check out ✨ "RAILS_ENV=demo" (RailsConf 2022) ✨:

Table of Contents

  • Getting Started
    • Installation
    • App-Specific Setup
  • Defining Personas
  • Customizing the Design
  • Optional Features
    • The "Sign Up" Link
    • The "Display Credentials" feature
    • Developer CLI
    • Callbacks
    • Non-User Personas
    • FactoryBot sequence extension
  • Deploying a demo environment to the cloud
    • How to avoid breaking your new "demo" env
  • How to Contribute
    • Suggested Workflow

Getting Started

To get started, add the gem to your Gemfile and run bundle install:

gem 'demo_mode'


Then, run the installer and the installed migrations:

bundle exec rails generate demo_mode:install
bundle exec rails db:migrate

The installer will create a config file (at config/initializers/demo_mode.rb) and a sample persona (at config/personas/sample_persona.rb). You can ignore the initializer file for now (it will be covered in the "Additional Setup" section below).

You should, however, edit the sample persona and fill in the sign_in_as block (don't worry about anything elseβ€”you can read "Defining Personas" below once you're ready to add more personas):

sign_in_as do
  # Define your factory code here! For example:
  # FactoryBot.create(:user)

Next, "mount" the DemoMode engine at a route of your choice:

mount DemoMode::Engine => '/demo' # this will 404 unless Demo Mode is enabled

Finally, launch the app in Demo Mode by setting DEMO_MODE=1 in your environment:

DEMO_MODE=1 bundle exec rails s

You should now see your requests rerouted to the following page:

If not, don't panic! Your app may need a bit of extra setup in order for the gem to work as expected, so continue on to the "App-Specific Setup" section.

Otherwise, if everything seems to be working, skip down to "Defining Personas" to add more personas, or "Customizing the Design" to add your own logo/colors/styles to the UI. There are also a few "Optional Features" to explore. And if you'd like to deploy a "demo" version of your app somewhere, check out "Deploying a demo environment to the cloud".

App-Specific Setup

Depending on the conventions of your application, you may need to set a few extra values in your config/initializers/demo_mode.rb file.

1. Tell Demo Mode how to find your "current user"

Demo Mode assumes that your controllers define a conventional current_user method. If your app uses something other than current_user, you may tell it which method to call:

DemoMode.configure do
  current_user_method :current_human

2. Ensure that you have sign_in and sign_out methods

If your controllers do not already define sign_in and/or sign_out methods, define these methods and point them to your true sign-in/sign-out behaviors:

# in your `app/controllers/application_controller.rb`:

def sign_in(signinable)
  # log_in!(user: signinable)

def sign_out
  # log_out!

3. Make sure ActiveJob is configured (and running)

In order to use the persona picker UI, your application must be capable of running ActiveJob-based jobs. Read this guide to get started with ActiveJob.

If you're stuck on a loading spinner, you probably need to start a background job worker, which will depend on your selected backend (e.g. rake jobs:work, etc).

By default, Demo Mode will subclass its job off of ActiveJob::Base. If you want to supply your own base job class, simply uncomment and update this config:

DemoMode.configure do
  base_job_name 'MyApplicationJob' # any ActiveJob-compliant class name

4. Tell Demo Mode which controllers to use

By default, Demo Mode will take over ApplicationController (and all of its descendants), ensuring that any unauthenticated request is re-routed to the persona picker. This may not be the preferred behavior (if, for example, all you care about is rerouting the login page), so you can change this default:

DemoMode.configure do
  app_base_controller_name 'SignInsController' # or any controller of your choice

Alternatively, specific controllers can be excluded from this behavior by adding the following line at the top:

skip_before_action :demo_splash!, raise: false

Finally, when rendering the persona picker itself, Demo Mode will subclass itself off of ActionController::Base. If you'd rather use/define your own base controller for the demo splash page, you can supply its name:

DemoMode.configure do
  splash_base_controller_name 'MyDemoModeBaseController'

5. Accommodate uniqueness constraints & validations

When generating users on the fly, it is common to run into issues with UNIQUE constraints. (e.g. If each user must have a unique email, your user-generation code must account for this and generate a unique email each time.) If you are using factory_bot, you will want to enable our sequence patch, but be mindful of the known issues.

Still stuck?

If none of the above gets your "persona picker" into a working state, feel free to add an issue with as many specifics and screenshots as you can provide.

Defining Personas

The demo_mode:install generator will install an empty persona at config/personas/sample_persona.rb. By default, the file path will dictate the name of the persona (via .titleize), and any persona files you create within config/personas/ will automatically appear on the persona picker page (one persona per file).

Of course, you can always override the name by passing it to the generate_persona method:

DemoMode.generate_persona 'My Custom Name' do
  # ...

Within the generate_persona block, you will need to fill in the sign_in_as block with your "factory" code of choice:

sign_in_as { FactoryBot.create(:user) }

You should also specify a list of features to be displayed alongside the persona name:

features << '1 blog post'
features << '3 comments'

Personas up at the top (with user icons) are called "callout" personas and have callout true declared:

callout true

Personas without callout true (or with callout false) will show up without icons, and will appear instead in a searchable/filterable table, making it easy to support a large number of personas. That said, if your list of personas is getting too long, you can instead define multiple sign_in_as blocks as "variants" of a single persona, which will give them a select dropdown in the UI:

variant :pending_invite do
  sign_in_as { FactoryBot.create(:user, :pending_invite) }

If defined, the non-variant sign_in_as will show up as "default" in the dropdown.

Customizing the Design

To supply your own branding, you can override the logo (in the upper left), the loading spinner (shown during persona generation), and the default persona icon:

DemoMode.configure do
  logo { image_tag('my-company-logo.svg') }
  loader { render partial: 'shared/loading_spinner' }

  # change the default persona icon to something else:
  icon 'path/to/icon.png'

  # `icon` may alternatively accept a block for arbitrary rendering:
  icon do
    # Any view helpers are available in this context.

  # ...

Individual personas also support the icon option, and come with three built-in options:

DemoMode.add_persona do
  callout true # icons only apply to "callout" personas

  # Use a symbol for a built-in: `:user` (default), `:users`, and `:tophat`
  icon :tophat

  # Or, again, supply your own icon with a string or block:
  icon 'path/to/my/icon.png'
  icon { image_tag('images/dancing-penguin.gif') }

  # ...

To customize or override the CSS entirely, create your own application.css file at app/assets/stylesheets/demo_mode/application.css:

 *= require demo_mode/normalize
 *= require demo_mode/default
 *= require_self

/* Use CSS variables to override the default font and colors: */
:root {
  --font-family: Papyrus, fantasy; 
  --primary-color: red;

You can put anything you want in there! The persona picker UI is constructed largely with semantic markup and is intended to be easy to customize or style from scratch.

Optional Features

Your config/initializers/demo_mode.rb will be generated with many commented-out lines. Here are a few optional features you might consider un-commenting:

The "Sign Up" Link

To show a "sign up" link in the upper right of the splash page, provide your sign_up_path like so:

DemoMode.configure do
  sign_up_path { new_account_path } # or any Rails route

You'll need to make sure that any sign-up-related controllers are excluded from the splash page redirect, via a skip_before_action or by changing the app_base_controller_name config. See the controller configuration instructions above for detailed instructions!

The "Display Credentials" feature

You may optionally display the account's credentials as an extra step, prior to signing in. This comes with the option to "sign in manually" (via your app's login form), and can be useful for stepping through login features like multi-factor authentication (which would otherwise be skipped by the persona picker):

DemoMode.configure do
  sign_in_path { login_path } # tell Demo Mode where your login path is

You may also toggle this feature on or off on a per-persona basis:

DemoMode.add_persona do
  display_credentials false

By default, Demo Mode will generate a new password for you. Make sure that you actually make use of DemoMode.current_password when constructing your user:

DemoMode.add_persona do
  sign_in_as do
    User.create(..., password: DemoMode.current_password)

You may also define your own "password generator":

DemoMode.configure do
  # very random password:
  password { SecureRandom.uuid }

  # or always the same password:
  password { "RailsConf2022" }

Developer CLI

Demo Mode ships with a developer-friendly CLI! Simply run the following, and follow the interactive prompt to generate an account:

bundle exec rake persona:create

This will generate the account and output the sign-in credentials:

┏━━ β­‘ Basic User β­‘ ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
┃ πŸ‘€ ::
┃ πŸ”‘ :: aReallyCoolPassword
┗━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ (0.0s) ━

Much like the "Display Credentials" feature above, you'll need to make use of DemoMode.current_password in your personas (and/or customize the default password generator) in order for these credentials to be valid!

You can customize the rake task's name within your app's Rakefile:

task create_user: 'persona:create'


You may choose to wrap persona generation with some additional logic. Say, for example, you want to set some extra global state, or run some code that modifies every persona you generate:

DemoMode.configure do
  around_persona_generation do |generator| do |account|
      account.update!(metadata: '123')

You must run and return the "signinable" object from the callback block.

Non-User Personas

Sometimes the thing you want to demo isn't something a logged-in user would see, but also isn't something accessible to any visitor. For example, maybe your app supports private invite tokens, and you'd like to have a persona that generates a token and links to this exclusive "sign up" behavior.

To do this, you can define a persona that returns some other object in its sign_in_as block. For example, let's return an invite token:

sign_in_as do

Then, you can define a custom begin_demo behavior. This will replace the usual sign_in(...) call with anything of your choice, and the model we generated above is accessible as @session.signinable:

begin_demo do
  redirect_to sign_up_path(invite: @session.signinable.invite_token)

FactoryBot sequence extension

DemoMode comes with a patch designed to be a drop-in replacement for factory_bot's sequence feature, ensuring that sequences like this...

sequence(:column_name) { |i| "Something #{i}" }

...will continue working across Ruby processes even after there are existing records in the DB (rather than starting at "Something 1" each time). This feature is necessary wherever you rely on UNIQUE constraints in the database, or uniqueness validations on your models.

This patch must be manually loaded after loading FactoryBot:

require 'factory_bot'
require 'demo_mode/factory_bot_ext'


  • The sequences extension is not concurrency-safe, so if you run multiple server threads/processes, you will want to take out a mutex prior to generating each persona:

    DemoMode.configure do
      # ...
      around_persona_generation do |generator|
        # Here we rely on
        ActiveRecord::Base.with_advisory_lock('demo_mode') do

  • The sequences extension does not play well with deletions, since it may encounter these gaps and assume it has reached the next starting value. If your application must support deletions on models with sequences, the recommended workaround is to remove the impacted UNIQUE constraints (only in your deployed demo/sandbox instances, of course) and conditionally disable any uniqueness validations (e.g. validates ... unless DemoMode.enabled?).

Deploying a demo environment to the cloud

This gem truly shines when used to deploy a "demo" version of your app to the cloud!

While the details of a custom environment deployment will vary from app to app, you can get started by simply adding a demo.rb file to your config/environments folder:

Rails.application.configure do
  ENV['DEMO_MODE'] = true

  # Recommended production-like behaviors:
  config.cache_classes = true
  config.eager_load = true
  config.consider_all_requests_local = false
  config.action_controller.perform_caching = true
  config.assets.compile = false
  config.assets.unknown_asset_fallback = false
  config.assets.digest = true
  config.force_ssl = true
  config.action_dispatch.show_exceptions = false

  # Recommended development/test-like behaviors:
  config.action_mailer.raise_delivery_errors = false
  config.action_mailer.perform_deliveries = false

We recommend using production-like caching/precompiling, but be sure to use test/development-like configurations for emails and any external HTTP requests / API connections! If you currently have no way of stubbing out these behaviors, we strongly encourage configuring your app to use webvalve before you attempt to set up a demo environment.

With the above environment configured, you can now launch your app in this mode:

RAILS_ENV=demo bundle exec rails s

(Remember that you can always launch your app with DEMO_MODE=true, regardless of the Rails environment, so don't worry about RAILS_ENV until it's time to deploy something somewhere.)

How to avoid breaking your new "demo" env

Step 1: Tests!

It's strongly suggested that you build end-to-end integration/feature tests into your application's test suite. You can toggle ENV['DEMO_MODE'] on and off directly from within tests, or, if you use RSpec, you can enable Demo Mode with the following before block:

before do
  allow(DemoMode).to receive(:enabled?).and_return(true)

Then, write a test that actually exercises the persona sign-in flow and steps through your app experience as that persona:

scenario 'an important product demo' do
  expect(demo_loading_page).to be_loaded

  expect(dashboard_page).to be_loaded
  expect(dashboard_page).to have_blog_posts(count: 1)
  # etc ...

This ensures that your demo personas are tested as part of your tests locally and in CI, and if your tests step carefully through the pages that are typically demoed, you can be more confident that changes to your app won't lead to surprise breakages in your demo-enabled environments.

You may also wish to add a "unit" tests to ensure that each persona can be generated on its own and doesn't rely on hardcoded values for uniqueness:

DemoMode.personas.each do |persona|
  persona.variants.keys.each do |variant|
    RSpec.describe("Persona: '#{}', '#{variant}'") do
      it 'can be generated twice in a row' do
        persona.generate!(variant: variant)
        persona.generate!(variant: variant)

Step 2: Monitoring!

Finally, once you've deployed your demo environment, we encourage you to monitor it the same way you would your production instance. (This is especially important if you use this environment to deliver live product demos to other humans!)

Exceptions should be configured to go to your error tracker, alerts should still be wired up to ping your engineers, and if you operate an "on call" process, engineers should be made aware that this demo environment is a "production-like" environment and should expect "production-like" uptime guarantees.

Again, to learn more about how we use and operate our "demo" environments at Betterment, check out our ✨ RailsConf 2022 talk entitled "RAILS_ENV=demo" ✨!

How to Contribute

We would love for you to contribute! Anything that benefits the majority of demo_mode usersβ€”from a documentation fix to an entirely new featureβ€”is encouraged.

Before diving in, check our issue tracker and consider creating a new issue to get early feedback on your proposed change.

Suggested Workflow

  • Fork the project and create a new branch for your contribution.
  • Write your contribution (and any applicable test coverage).
  • Make sure all tests pass (bundle exec rake).
  • Submit a pull request.