Installed devise and created devise User model

app/models/user.rb

+class User < ApplicationRecord
+  # Include default devise modules. Others available are:
+  # :confirmable, :lockable, :timeoutable and :omniauthable
+  devise :database_authenticatable, :registerable,
+         :recoverable, :rememberable, :trackable, :validatable
+end

config/initializers/devise.rb

+# frozen_string_literal: true
+
+# Use this hook to configure devise mailer, warden hooks and so forth.
+# Many of these configuration options can be set straight in your model.
+Devise.setup do |config|
+  # The secret key used by Devise. Devise uses this key to generate
+  # random tokens. Changing this key will render invalid all existing
+  # confirmation, reset password and unlock tokens in the database.
+  # Devise will use the `secret_key_base` as its `secret_key`
+  # by default. You can change it below and use your own secret key.
+  # config.secret_key = 'e5fd3666bfb824026126e6f1a7d4cf010d2c63fc746b6c8ab5c809a805bf672ef2b9e5e62a10d03dd6838e008c154b943255507b2c1f4cf80788761e4e526853'
+  
+  # ==> Controller configuration
+  # Configure the parent class to the devise controllers.
+  # config.parent_controller = 'DeviseController'
+
+  # ==> Mailer Configuration
+  # Configure the e-mail address which will be shown in Devise::Mailer,
+  # note that it will be overwritten if you use your own mailer class
+  # with default "from" parameter.
+  config.mailer_sender = 'please-change-me-at-config-initializers-devise@example.com'
+
+  # Configure the class responsible to send e-mails.
+  # config.mailer = 'Devise::Mailer'
+
+  # Configure the parent class responsible to send e-mails.
+  # config.parent_mailer = 'ActionMailer::Base'
+
+  # ==> ORM configuration
+  # Load and configure the ORM. Supports :active_record (default) and
+  # :mongoid (bson_ext recommended) by default. Other ORMs may be
+  # available as additional gems.
+  require 'devise/orm/active_record'
+
+  # ==> Configuration for any authentication mechanism
+  # Configure which keys are used when authenticating a user. The default is
+  # just :email. You can configure it to use [:username, :subdomain], so for
+  # authenticating a user, both parameters are required. Remember that those
+  # parameters are used only when authenticating and not when retrieving from
+  # session. If you need permissions, you should implement that in a before filter.
+  # You can also supply a hash where the value is a boolean determining whether
+  # or not authentication should be aborted when the value is not present.
+  # config.authentication_keys = [:email]
+
+  # Configure parameters from the request object used for authentication. Each entry
+  # given should be a request method and it will automatically be passed to the
+  # find_for_authentication method and considered in your model lookup. For instance,
+  # if you set :request_keys to [:subdomain], :subdomain will be used on authentication.
+  # The same considerations mentioned for authentication_keys also apply to request_keys.
+  # config.request_keys = []
+
+  # Configure which authentication keys should be case-insensitive.
+  # These keys will be downcased upon creating or modifying a user and when used
+  # to authenticate or find a user. Default is :email.
+  config.case_insensitive_keys = [:email]
+
+  # Configure which authentication keys should have whitespace stripped.
+  # These keys will have whitespace before and after removed upon creating or
+  # modifying a user and when used to authenticate or find a user. Default is :email.
+  config.strip_whitespace_keys = [:email]
+
+  # Tell if authentication through request.params is enabled. True by default.
+  # It can be set to an array that will enable params authentication only for the
+  # given strategies, for example, `config.params_authenticatable = [:database]` will
+  # enable it only for database (email + password) authentication.
+  # config.params_authenticatable = true
+
+  # Tell if authentication through HTTP Auth is enabled. False by default.
+  # It can be set to an array that will enable http authentication only for the
+  # given strategies, for example, `config.http_authenticatable = [:database]` will
+  # enable it only for database authentication. The supported strategies are:
+  # :database      = Support basic authentication with authentication key + password
+  # config.http_authenticatable = false
+
+  # If 401 status code should be returned for AJAX requests. True by default.
+  # config.http_authenticatable_on_xhr = true
+
+  # The realm used in Http Basic Authentication. 'Application' by default.
+  # config.http_authentication_realm = 'Application'
+
+  # It will change confirmation, password recovery and other workflows
+  # to behave the same regardless if the e-mail provided was right or wrong.
+  # Does not affect registerable.
+  # config.paranoid = true
+
+  # By default Devise will store the user in session. You can skip storage for
+  # particular strategies by setting this option.
+  # Notice that if you are skipping storage for all authentication paths, you
+  # may want to disable generating routes to Devise's sessions controller by
+  # passing skip: :sessions to `devise_for` in your config/routes.rb
+  config.skip_session_storage = [:http_auth]
+
+  # By default, Devise cleans up the CSRF token on authentication to
+  # avoid CSRF token fixation attacks. This means that, when using AJAX
+  # requests for sign in and sign up, you need to get a new CSRF token
+  # from the server. You can disable this option at your own risk.
+  # config.clean_up_csrf_token_on_authentication = true
+
+  # When false, Devise will not attempt to reload routes on eager load.
+  # This can reduce the time taken to boot the app but if your application
+  # requires the Devise mappings to be loaded during boot time the application
+  # won't boot properly.
+  # config.reload_routes = true
+
+  # ==> Configuration for :database_authenticatable
+  # For bcrypt, this is the cost for hashing the password and defaults to 11. If
+  # using other algorithms, it sets how many times you want the password to be hashed.
+  #
+  # Limiting the stretches to just one in testing will increase the performance of
+  # your test suite dramatically. However, it is STRONGLY RECOMMENDED to not use
+  # a value less than 10 in other environments. Note that, for bcrypt (the default
+  # algorithm), the cost increases exponentially with the number of stretches (e.g.
+  # a value of 20 is already extremely slow: approx. 60 seconds for 1 calculation).
+  config.stretches = Rails.env.test? ? 1 : 11
+
+  # Set up a pepper to generate the hashed password.
+  # config.pepper = 'baafaedb6fb560468acc6ca4d4949f044d5e808525665eacaee747b622c101feea531b9746f7d063f05005d30d3b143505ffd44055c27c5c1f0ce41b23a17103'
+
+  # Send a notification to the original email when the user's email is changed.
+  # config.send_email_changed_notification = false
+
+  # Send a notification email when the user's password is changed.
+  # config.send_password_change_notification = false
+
+  # ==> Configuration for :confirmable
+  # A period that the user is allowed to access the website even without
+  # confirming their account. For instance, if set to 2.days, the user will be
+  # able to access the website for two days without confirming their account,
+  # access will be blocked just in the third day. Default is 0.days, meaning
+  # the user cannot access the website without confirming their account.
+  # config.allow_unconfirmed_access_for = 2.days
+
+  # A period that the user is allowed to confirm their account before their
+  # token becomes invalid. For example, if set to 3.days, the user can confirm
+  # their account within 3 days after the mail was sent, but on the fourth day
+  # their account can't be confirmed with the token any more.
+  # Default is nil, meaning there is no restriction on how long a user can take
+  # before confirming their account.
+  # config.confirm_within = 3.days
+
+  # If true, requires any email changes to be confirmed (exactly the same way as
+  # initial account confirmation) to be applied. Requires additional unconfirmed_email
+  # db field (see migrations). Until confirmed, new email is stored in
+  # unconfirmed_email column, and copied to email column on successful confirmation.
+  config.reconfirmable = true
+
+  # Defines which key will be used when confirming an account
+  # config.confirmation_keys = [:email]
+
+  # ==> Configuration for :rememberable
+  # The time the user will be remembered without asking for credentials again.
+  # config.remember_for = 2.weeks
+
+  # Invalidates all the remember me tokens when the user signs out.
+  config.expire_all_remember_me_on_sign_out = true
+
+  # If true, extends the user's remember period when remembered via cookie.
+  # config.extend_remember_period = false
+
+  # Options to be passed to the created cookie. For instance, you can set
+  # secure: true in order to force SSL only cookies.
+  # config.rememberable_options = {}
+
+  # ==> Configuration for :validatable
+  # Range for password length.
+  config.password_length = 6..128
+
+  # Email regex used to validate email formats. It simply asserts that
+  # one (and only one) @ exists in the given string. This is mainly
+  # to give user feedback and not to assert the e-mail validity.
+  config.email_regexp = /\A[^@\s]+@[^@\s]+\z/
+
+  # ==> Configuration for :timeoutable
+  # The time you want to timeout the user session without activity. After this
+  # time the user will be asked for credentials again. Default is 30 minutes.
+  # config.timeout_in = 30.minutes
+
+  # ==> Configuration for :lockable
+  # Defines which strategy will be used to lock an account.
+  # :failed_attempts = Locks an account after a number of failed attempts to sign in.
+  # :none            = No lock strategy. You should handle locking by yourself.
+  # config.lock_strategy = :failed_attempts
+
+  # Defines which key will be used when locking and unlocking an account
+  # config.unlock_keys = [:email]
+
+  # Defines which strategy will be used to unlock an account.
+  # :email = Sends an unlock link to the user email
+  # :time  = Re-enables login after a certain amount of time (see :unlock_in below)
+  # :both  = Enables both strategies
+  # :none  = No unlock strategy. You should handle unlocking by yourself.
+  # config.unlock_strategy = :both
+
+  # Number of authentication tries before locking an account if lock_strategy
+  # is failed attempts.
+  # config.maximum_attempts = 20
+
+  # Time interval to unlock the account if :time is enabled as unlock_strategy.
+  # config.unlock_in = 1.hour
+
+  # Warn on the last attempt before the account is locked.
+  # config.last_attempt_warning = true
+
+  # ==> Configuration for :recoverable
+  #
+  # Defines which key will be used when recovering the password for an account
+  # config.reset_password_keys = [:email]
+
+  # Time interval you can reset your password with a reset password key.
+  # Don't put a too small interval or your users won't have the time to
+  # change their passwords.
+  config.reset_password_within = 6.hours
+
+  # When set to false, does not sign a user in automatically after their password is
+  # reset. Defaults to true, so a user is signed in automatically after a reset.
+  # config.sign_in_after_reset_password = true
+
+  # ==> Configuration for :encryptable
+  # Allow you to use another hashing or encryption algorithm besides bcrypt (default).
+  # You can use :sha1, :sha512 or algorithms from others authentication tools as
+  # :clearance_sha1, :authlogic_sha512 (then you should set stretches above to 20
+  # for default behavior) and :restful_authentication_sha1 (then you should set
+  # stretches to 10, and copy REST_AUTH_SITE_KEY to pepper).
+  #
+  # Require the `devise-encryptable` gem when using anything other than bcrypt
+  # config.encryptor = :sha512
+
+  # ==> Scopes configuration
+  # Turn scoped views on. Before rendering "sessions/new", it will first check for
+  # "users/sessions/new". It's turned off by default because it's slower if you
+  # are using only default views.
+  # config.scoped_views = false
+
+  # Configure the default scope given to Warden. By default it's the first
+  # devise role declared in your routes (usually :user).
+  # config.default_scope = :user
+
+  # Set this configuration to false if you want /users/sign_out to sign out
+  # only the current scope. By default, Devise signs out all scopes.
+  # config.sign_out_all_scopes = true
+
+  # ==> Navigation configuration
+  # Lists the formats that should be treated as navigational. Formats like
+  # :html, should redirect to the sign in page when the user does not have
+  # access, but formats like :xml or :json, should return 401.
+  #
+  # If you have any extra navigational formats, like :iphone or :mobile, you
+  # should add them to the navigational formats lists.
+  #
+  # The "*/*" below is required to match Internet Explorer requests.
+  # config.navigational_formats = ['*/*', :html]
+
+  # The default HTTP method used to sign out a resource. Default is :delete.
+  config.sign_out_via = :delete
+
+  # ==> OmniAuth
+  # Add a new OmniAuth provider. Check the wiki for more information on setting
+  # up on your models and hooks.
+  # config.omniauth :github, 'APP_ID', 'APP_SECRET', scope: 'user,public_repo'
+
+  # ==> Warden configuration
+  # If you want to use other strategies, that are not supported by Devise, or
+  # change the failure app, you can configure them inside the config.warden block.
+  #
+  # config.warden do |manager|
+  #   manager.intercept_401 = false
+  #   manager.default_strategies(scope: :user).unshift :some_external_strategy
+  # end
+
+  # ==> Mountable engine configurations
+  # When using Devise inside an engine, let's call it `MyEngine`, and this engine
+  # is mountable, there are some extra configurations to be taken into account.
+  # The following options are available, assuming the engine is mounted as:
+  #
+  #     mount MyEngine, at: '/my_engine'
+  #
+  # The router that invoked `devise_for`, in the example above, would be:
+  # config.router_name = :my_engine
+  #
+  # When using OmniAuth, Devise cannot automatically set OmniAuth path,
+  # so you need to do it manually. For the users scope, it would be:
+  # config.omniauth_path_prefix = '/my_engine/users/auth'
+end

config/locales/devise.en.yml

+# Additional translations at https://github.com/plataformatec/devise/wiki/I18n
+
+en:
+  devise:
+    confirmations:
+      confirmed: "Your email address has been successfully confirmed."
+      send_instructions: "You will receive an email with instructions for how to confirm your email address in a few minutes."
+      send_paranoid_instructions: "If your email address exists in our database, you will receive an email with instructions for how to confirm your email address in a few minutes."
+    failure:
+      already_authenticated: "You are already signed in."
+      inactive: "Your account is not activated yet."
+      invalid: "Invalid %{authentication_keys} or password."
+      locked: "Your account is locked."
+      last_attempt: "You have one more attempt before your account is locked."
+      not_found_in_database: "Invalid %{authentication_keys} or password."
+      timeout: "Your session expired. Please sign in again to continue."
+      unauthenticated: "You need to sign in or sign up before continuing."
+      unconfirmed: "You have to confirm your email address before continuing."
+    mailer:
+      confirmation_instructions:
+        subject: "Confirmation instructions"
+      reset_password_instructions:
+        subject: "Reset password instructions"
+      unlock_instructions:
+        subject: "Unlock instructions"
+      email_changed:
+        subject: "Email Changed"
+      password_change:
+        subject: "Password Changed"
+    omniauth_callbacks:
+      failure: "Could not authenticate you from %{kind} because \"%{reason}\"."
+      success: "Successfully authenticated from %{kind} account."
+    passwords:
+      no_token: "You can't access this page without coming from a password reset email. If you do come from a password reset email, please make sure you used the full URL provided."
+      send_instructions: "You will receive an email with instructions on how to reset your password in a few minutes."
+      send_paranoid_instructions: "If your email address exists in our database, you will receive a password recovery link at your email address in a few minutes."
+      updated: "Your password has been changed successfully. You are now signed in."
+      updated_not_active: "Your password has been changed successfully."
+    registrations:
+      destroyed: "Bye! Your account has been successfully cancelled. We hope to see you again soon."
+      signed_up: "Welcome! You have signed up successfully."
+      signed_up_but_inactive: "You have signed up successfully. However, we could not sign you in because your account is not yet activated."
+      signed_up_but_locked: "You have signed up successfully. However, we could not sign you in because your account is locked."
+      signed_up_but_unconfirmed: "A message with a confirmation link has been sent to your email address. Please follow the link to activate your account."
+      update_needs_confirmation: "You updated your account successfully, but we need to verify your new email address. Please check your email and follow the confirm link to confirm your new email address."
+      updated: "Your account has been updated successfully."
+    sessions:
+      signed_in: "Signed in successfully."
+      signed_out: "Signed out successfully."
+      already_signed_out: "Signed out successfully."
+    unlocks:
+      send_instructions: "You will receive an email with instructions for how to unlock your account in a few minutes."
+      send_paranoid_instructions: "If your account exists, you will receive an email with instructions for how to unlock it in a few minutes."
+      unlocked: "Your account has been unlocked successfully. Please sign in to continue."
+  errors:
+    messages:
+      already_confirmed: "was already confirmed, please try signing in"
+      confirmation_period_expired: "needs to be confirmed within %{period}, please request a new one"
+      expired: "has expired, please request a new one"
+      not_found: "not found"
+      not_locked: "was not locked"
+      not_saved:
+        one: "1 error prohibited this %{resource} from being saved:"
+        other: "%{count} errors prohibited this %{resource} from being saved:"

config/routes.rb

 Rails.application.routes.draw do
+  devise_for :users
 	resources :posts
   root to: 'posts#index'
 end
\ No newline at end of file

db/migrate/20180702141545_devise_create_users.rb

+# frozen_string_literal: true
+
+class DeviseCreateUsers < ActiveRecord::Migration[5.2]
+  def change
+    create_table :users do |t|
+      ## Database authenticatable
+      t.string :email,              null: false, default: ""
+      t.string :encrypted_password, null: false, default: ""
+
+      ## Recoverable
+      t.string   :reset_password_token
+      t.datetime :reset_password_sent_at
+
+      ## Rememberable
+      t.datetime :remember_created_at
+
+      ## Trackable
+      t.integer  :sign_in_count, default: 0, null: false
+      t.datetime :current_sign_in_at
+      t.datetime :last_sign_in_at
+      t.string   :current_sign_in_ip
+      t.string   :last_sign_in_ip
+
+      ## Confirmable
+      # t.string   :confirmation_token
+      # t.datetime :confirmed_at
+      # t.datetime :confirmation_sent_at
+      # t.string   :unconfirmed_email # Only if using reconfirmable
+
+      ## Lockable
+      # t.integer  :failed_attempts, default: 0, null: false # Only if lock strategy is :failed_attempts
+      # t.string   :unlock_token # Only if unlock strategy is :email or :both
+      # t.datetime :locked_at
+
+      t.string :first_name
+      t.string :last_name
+
+      t.timestamps null: false
+    end
+
+    add_index :users, :email,                unique: true
+    add_index :users, :reset_password_token, unique: true
+    # add_index :users, :confirmation_token,   unique: true
+    # add_index :users, :unlock_token,         unique: true
+  end
+end

test/fixtures/users.yml

+# Read about fixtures at http://api.rubyonrails.org/classes/ActiveRecord/FixtureSet.html
+
+# This model initially had no columns defined. If you add columns to the
+# model remove the '{}' from the fixture names and add the columns immediately
+# below each fixture, per the syntax in the comments below
+#
+one: {}
+# column: value
+#
+two: {}
+# column: value

test/models/user_test.rb

+require 'test_helper'
+
+class UserTest < ActiveSupport::TestCase
+  # test "the truth" do
+  #   assert true
+  # end
+end