diff --git a/.travis.yml b/.travis.yml
index e4e51f89c9b..952ad7a4467 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,5 +1,21 @@
 language: ruby
 
+env:
+  global:
+    - DISCOURSE_HOSTNAME=www.example.com
+    - RUBY_GC_MALLOC_LIMIT=50000000
+  matrix:
+    - "RAILS_MASTER=1"
+    - "RAILS_MASTER=0"
+
+matrix:
+  allow_failures:
+    - rvm: 2.0.0
+      env: "RAILS_MASTER=1"
+    - rvm: 2.1
+      env: "RAILS_MASTER=1"
+  fast_finish: true
+
 rvm:
   - 2.0.0
   - 2.1
@@ -11,11 +27,6 @@ sudo: false
 
 cache: bundler
 
-env:
-  global:
-    - DISCOURSE_HOSTNAME=www.example.com
-    - RUBY_GC_MALLOC_LIMIT=50000000
-
 before_install:
   - npm i -g jshint
   - jshint .
diff --git a/Gemfile b/Gemfile
index b3aa247122d..8f64452f800 100644
--- a/Gemfile
+++ b/Gemfile
@@ -4,7 +4,7 @@ source 'https://rubygems.org'
 
 module ::Kernel
   def rails_master?
-    ENV["RAILS_MASTER"]
+    ENV["RAILS_MASTER"] == '1'
   end
 end
 
@@ -71,11 +71,11 @@ gem 'seed-fu', '~> 2.3.3'
 
 if rails_master?
   gem 'rails', git: 'https://github.com/rails/rails.git'
-  gem 'actionpack-action_caching', git: 'https://github.com/rails/actionpack-action_caching.git'
 else
   gem 'rails'
-  gem 'actionpack-action_caching'
 end
+
+gem 'actionpack-action_caching'
 gem 'rails-observers'
 
 # Rails 4.1.6+ will relax the mail gem version requirement to `~> 2.5, >= 2.5.4`.
@@ -91,7 +91,11 @@ gem 'redis', require:  ["redis", "redis/connection/hiredis"]
 # We use some ams 0.8.0 features, need to amend code
 # to support 0.9 etc, bench needs to run and ensure no
 # perf regressions
-gem 'active_model_serializers', '~> 0.8.0'
+if rails_master?
+  gem 'active_model_serializers', github: 'rails-api/active_model_serializers', branch: '0-8-stable'
+else
+  gem 'active_model_serializers', '~> 0.8.0'
+end
 
 
 gem 'onebox'
diff --git a/Gemfile_master.lock b/Gemfile_master.lock
index 16e366b7caf..d3fce3147ed 100644
--- a/Gemfile_master.lock
+++ b/Gemfile_master.lock
@@ -1,63 +1,64 @@
 GIT
-  remote: https://github.com/rails/actionpack-action_caching.git
-  revision: a9f3f09477b12b51faa6756005eee4103f7f4030
+  remote: git://github.com/rails-api/active_model_serializers.git
+  revision: b6b01d0b7396f3deaa6e661cedf4bc5efe2f4525
+  branch: 0-8-stable
   specs:
-    actionpack-action_caching (1.1.0)
-      actionpack (>= 4.0.0, < 5.0)
+    active_model_serializers (0.8.2)
+      activemodel (>= 3.0)
 
 GIT
   remote: https://github.com/rails/rails.git
-  revision: 316962d0922992fbe756521bd7c94a751aa1253e
+  revision: aa6637d140c2ebd28bbd23fc250af033a065dbe8
   specs:
-    actionmailer (4.2.0.beta1)
-      actionpack (= 4.2.0.beta1)
-      actionview (= 4.2.0.beta1)
-      activejob (= 4.2.0.beta1)
+    actionmailer (4.2.0.beta4)
+      actionpack (= 4.2.0.beta4)
+      actionview (= 4.2.0.beta4)
+      activejob (= 4.2.0.beta4)
       mail (~> 2.5, >= 2.5.4)
-      rails-dom-testing (~> 1.0, >= 1.0.2)
-    actionpack (4.2.0.beta1)
-      actionview (= 4.2.0.beta1)
-      activesupport (= 4.2.0.beta1)
+      rails-dom-testing (~> 1.0, >= 1.0.4)
+    actionpack (4.2.0.beta4)
+      actionview (= 4.2.0.beta4)
+      activesupport (= 4.2.0.beta4)
       rack (~> 1.6.0.beta)
       rack-test (~> 0.6.2)
-      rails-dom-testing (~> 1.0, >= 1.0.2)
-      rails-html-sanitizer (~> 1.0)
-    actionview (4.2.0.beta1)
-      activesupport (= 4.2.0.beta1)
+      rails-dom-testing (~> 1.0, >= 1.0.4)
+      rails-html-sanitizer (~> 1.0, >= 1.0.1)
+    actionview (4.2.0.beta4)
+      activesupport (= 4.2.0.beta4)
       builder (~> 3.1)
       erubis (~> 2.7.0)
-      rails-dom-testing (~> 1.0, >= 1.0.2)
-      rails-html-sanitizer (~> 1.0)
-    activejob (4.2.0.beta1)
-      activesupport (= 4.2.0.beta1)
-      globalid (>= 0.2.3)
-    activemodel (4.2.0.beta1)
-      activesupport (= 4.2.0.beta1)
+      rails-dom-testing (~> 1.0, >= 1.0.4)
+      rails-html-sanitizer (~> 1.0, >= 1.0.1)
+    activejob (4.2.0.beta4)
+      activesupport (= 4.2.0.beta4)
+      globalid (>= 0.3.0)
+    activemodel (4.2.0.beta4)
+      activesupport (= 4.2.0.beta4)
       builder (~> 3.1)
-    activerecord (4.2.0.beta1)
-      activemodel (= 4.2.0.beta1)
-      activesupport (= 4.2.0.beta1)
-      arel (>= 6.0.0.beta1, < 6.1)
-    activesupport (4.2.0.beta1)
+    activerecord (4.2.0.beta4)
+      activemodel (= 4.2.0.beta4)
+      activesupport (= 4.2.0.beta4)
+      arel (>= 6.0.0.beta2, < 6.1)
+    activesupport (4.2.0.beta4)
       i18n (>= 0.7.0.beta1, < 0.8)
       json (~> 1.7, >= 1.7.7)
       minitest (~> 5.1)
       thread_safe (~> 0.1)
       tzinfo (~> 1.1)
-    rails (4.2.0.beta1)
-      actionmailer (= 4.2.0.beta1)
-      actionpack (= 4.2.0.beta1)
-      actionview (= 4.2.0.beta1)
-      activejob (= 4.2.0.beta1)
-      activemodel (= 4.2.0.beta1)
-      activerecord (= 4.2.0.beta1)
-      activesupport (= 4.2.0.beta1)
+    rails (4.2.0.beta4)
+      actionmailer (= 4.2.0.beta4)
+      actionpack (= 4.2.0.beta4)
+      actionview (= 4.2.0.beta4)
+      activejob (= 4.2.0.beta4)
+      activemodel (= 4.2.0.beta4)
+      activerecord (= 4.2.0.beta4)
+      activesupport (= 4.2.0.beta4)
       bundler (>= 1.3.0, < 2.0)
-      railties (= 4.2.0.beta1)
+      railties (= 4.2.0.beta4)
       sprockets-rails (~> 3.0.0.beta1)
-    railties (4.2.0.beta1)
-      actionpack (= 4.2.0.beta1)
-      activesupport (= 4.2.0.beta1)
+    railties (4.2.0.beta4)
+      actionpack (= 4.2.0.beta4)
+      activesupport (= 4.2.0.beta4)
       rake (>= 0.8.7)
       thor (>= 0.18.1, < 2.0)
 
@@ -79,16 +80,13 @@ PATH
 GEM
   remote: https://rubygems.org/
   specs:
-    active_model_serializers (0.8.2)
-      activemodel (>= 3.0)
+    actionpack-action_caching (1.1.1)
+      actionpack (>= 4.0.0, < 5.0)
     addressable (2.3.6)
-    airbrake (3.1.2)
-      activesupport
-      builder
     annotate (2.6.5)
       activerecord (>= 2.3.0)
       rake (>= 0.8.7)
-    arel (6.0.0.beta1)
+    arel (6.0.0.beta2)
     barber (0.4.2)
       ember-source
       execjs
@@ -114,25 +112,25 @@ GEM
       dotenv-deployment (~> 0.0.2)
     dotenv-deployment (0.0.2)
     email_reply_parser-discourse (0.6)
-    ember-data-source (1.0.0.beta.9)
+    ember-data-source (0.14)
       ember-source
-    ember-rails (0.15.0)
+    ember-rails (0.14.1)
       active_model_serializers
       barber (>= 0.4.1)
-      ember-data-source (>= 1.0.0.beta.5)
-      ember-source (>= 1.1.0)
+      ember-data-source
+      ember-source
       execjs (>= 1.2)
-      handlebars-source (> 1.0.0)
+      handlebars-source
       jquery-rails (>= 1.0.17)
       railties (>= 3.1)
     ember-source (1.6.0.beta.2)
       handlebars-source (~> 1.0)
     erubis (2.7.0)
     eventmachine (1.0.3)
-    excon (0.39.5)
+    excon (0.39.6)
     execjs (2.2.1)
     exifr (1.1.3)
-    fabrication (2.11.3)
+    fabrication (2.9.8)
     fakeweb (1.3.0)
     faraday (0.9.0)
       multipart-post (>= 1.2, < 3)
@@ -146,7 +144,7 @@ GEM
     fast_xs (0.8.0)
     fastimage (1.6.3)
       addressable (~> 2.3, >= 2.3.5)
-    ffi (1.9.3)
+    ffi (1.9.5)
     flamegraph (0.0.5)
       fast_stack
     fog (1.22.1)
@@ -155,7 +153,7 @@ GEM
       fog-json
       ipaddress (~> 0.5)
       nokogiri (~> 1.5, >= 1.5.11)
-    fog-brightbox (0.5.0)
+    fog-brightbox (0.5.1)
       fog-core (~> 1.22)
       fog-json
       inflecto
@@ -176,7 +174,7 @@ GEM
     gctools (0.2.3)
     given_core (3.5.4)
       sorcerer (>= 0.3.7)
-    globalid (0.2.3)
+    globalid (0.3.0)
       activesupport (>= 4.1.0)
     guess_html_encoding (0.0.9)
     handlebars-source (1.3.0)
@@ -205,7 +203,7 @@ GEM
     librarian (0.1.2)
       highline
       thor (~> 0.15)
-    libv8 (3.16.14.3)
+    libv8 (3.16.14.7)
     listen (0.7.3)
     logster (0.1.6)
     loofah (2.0.1)
@@ -215,15 +213,15 @@ GEM
       mime-types (~> 1.16)
       treetop (~> 1.4.8)
     memory_profiler (0.0.4)
-    message_bus (0.9.5)
+    message_bus (1.0.5)
       eventmachine
       rack (>= 1.1.3)
       redis
     metaclass (0.0.4)
     method_source (0.8.2)
     mime-types (1.25.1)
-    mini_portile (0.6.0)
-    minitest (5.4.1)
+    mini_portile (0.6.1)
+    minitest (5.4.2)
     mocha (1.1.0)
       metaclass (~> 0.0.1)
     mock_redis (0.13.2)
@@ -237,8 +235,8 @@ GEM
       net-ssh (>= 2.6.5)
     net-ssh (2.9.1)
     netrc (0.7.7)
-    nokogiri (1.6.3.1)
-      mini_portile (= 0.6.0)
+    nokogiri (1.6.4.1)
+      mini_portile (~> 0.6.0)
     nokogumbo (1.1.12)
       nokogiri
     oauth (0.4.7)
@@ -274,7 +272,7 @@ GEM
     omniauth-twitter (1.0.1)
       multi_json (~> 1.3)
       omniauth-oauth (~> 1.0)
-    onebox (1.4.9)
+    onebox (1.5.3)
       moneta (~> 0.7)
       multi_json (~> 1.7)
       mustache (~> 0.99)
@@ -293,7 +291,7 @@ GEM
       pry (>= 0.9.10, < 0.11.0)
     pry-rails (0.3.2)
       pry (>= 0.9.10)
-    puma (2.9.0)
+    puma (2.9.1)
       rack (>= 1.1, < 2.0)
     qunit-rails (0.0.7)
       railties
@@ -307,13 +305,13 @@ GEM
       rack
     rack-test (0.6.2)
       rack (>= 1.0)
-    rails-deprecated_sanitizer (1.0.2)
+    rails-deprecated_sanitizer (1.0.3)
       activesupport (>= 4.2.0.alpha)
-    rails-dom-testing (1.0.2)
-      activesupport
+    rails-dom-testing (1.0.4)
+      activesupport (>= 4.2.0.beta, < 5.0)
       nokogiri (~> 1.6.0)
       rails-deprecated_sanitizer (>= 1.0.1)
-    rails-html-sanitizer (1.0.0)
+    rails-html-sanitizer (1.0.1)
       loofah (~> 2.0)
     rails-observers (0.1.2)
       activemodel (~> 4.0)
@@ -338,29 +336,28 @@ GEM
       netrc (~> 0.7)
     rinku (1.7.3)
     rmmseg-cpp (0.2.9)
-    rspec (3.0.0)
-      rspec-core (~> 3.0.0)
-      rspec-expectations (~> 3.0.0)
-      rspec-mocks (~> 3.0.0)
-    rspec-core (3.0.4)
-      rspec-support (~> 3.0.0)
-    rspec-expectations (3.0.4)
-      diff-lcs (>= 1.2.0, < 2.0)
-      rspec-support (~> 3.0.0)
+    rspec (2.99.0)
+      rspec-core (~> 2.99.0)
+      rspec-expectations (~> 2.99.0)
+      rspec-mocks (~> 2.99.0)
+    rspec-collection_matchers (1.0.0)
+      rspec-expectations (>= 2.99.0.beta1)
+    rspec-core (2.99.2)
+    rspec-expectations (2.99.2)
+      diff-lcs (>= 1.1.3, < 2.0)
     rspec-given (3.5.4)
       given_core (= 3.5.4)
       rspec (>= 2.12)
-    rspec-mocks (3.0.4)
-      rspec-support (~> 3.0.0)
-    rspec-rails (3.0.2)
+    rspec-mocks (2.99.2)
+    rspec-rails (2.99.0)
       actionpack (>= 3.0)
+      activemodel (>= 3.0)
       activesupport (>= 3.0)
       railties (>= 3.0)
-      rspec-core (~> 3.0.0)
-      rspec-expectations (~> 3.0.0)
-      rspec-mocks (~> 3.0.0)
-      rspec-support (~> 3.0.0)
-    rspec-support (3.0.4)
+      rspec-collection_matchers
+      rspec-core (~> 2.99.0)
+      rspec-expectations (~> 2.99.0)
+      rspec-mocks (~> 2.99.0)
     rtlit (0.0.5)
     ruby-openid (2.5.0)
     ruby-readability (0.7.0)
@@ -370,7 +367,7 @@ GEM
       crass (~> 0.2.0)
       nokogiri (>= 1.4.4)
       nokogumbo (= 1.1.12)
-    sass (3.4.2)
+    sass (3.2.19)
     seed-fu (2.3.3)
       activerecord (>= 3.1, < 4.2)
       activesupport (>= 3.1, < 4.2)
@@ -380,16 +377,16 @@ GEM
     shoulda-context (1.2.1)
     shoulda-matchers (2.7.0)
       activesupport (>= 3.0.0)
-    sidekiq (3.2.3)
-      celluloid (>= 0.15.2)
+    sidekiq (3.2.5)
+      celluloid (= 0.15.2)
       connection_pool (>= 2.0.0)
       json
       redis (>= 3.0.6)
       redis-namespace (>= 1.3.1)
     simple-rss (1.3.1)
-    simplecov (0.9.0)
+    simplecov (0.9.1)
       docile (~> 1.1.0)
-      multi_json
+      multi_json (~> 1.0)
       simplecov-html (~> 0.8.0)
     simplecov-html (0.8.0)
     sinatra (1.4.5)
@@ -402,7 +399,7 @@ GEM
     spork-rails (4.0.0)
       rails (>= 3.0.0, < 5)
       spork (>= 1.0rc0)
-    sprockets (2.12.1)
+    sprockets (2.12.3)
       hike (~> 1.2)
       multi_json (~> 1.0)
       rack (~> 1.0)
@@ -445,9 +442,8 @@ PLATFORMS
   ruby
 
 DEPENDENCIES
-  actionpack-action_caching!
-  active_model_serializers (~> 0.8.0)
-  airbrake (= 3.1.2)
+  actionpack-action_caching
+  active_model_serializers!
   annotate
   barber
   better_errors
@@ -457,7 +453,7 @@ DEPENDENCIES
   ember-rails
   ember-source (= 1.6.0.beta.2)
   eventmachine
-  fabrication
+  fabrication (= 2.9.8)
   fakeweb (~> 1.3.0)
   fast_blank
   fast_xor
@@ -514,6 +510,7 @@ DEPENDENCIES
   rest-client
   rinku
   rmmseg-cpp
+  rspec (= 2.99.0)
   rspec-given
   rspec-rails
   rtlit
diff --git a/app/models/concerns/has_custom_fields.rb b/app/models/concerns/has_custom_fields.rb
index cd9349539bd..cfe0db59040 100644
--- a/app/models/concerns/has_custom_fields.rb
+++ b/app/models/concerns/has_custom_fields.rb
@@ -12,7 +12,7 @@ module HasCustomFields
       end
     end
 
-    CUSTOM_FIELD_TRUE = ['t','true', 'T', 'True', 'TRUE'].freeze unless defined? CUSTOM_FIELD_TRUE
+    CUSTOM_FIELD_TRUE = ['1', 't', 'true', 'T', 'True', 'TRUE'].freeze unless defined? CUSTOM_FIELD_TRUE
 
     def self.cast_custom_field(key, value, types)
       return value unless types && type = types[key]
diff --git a/app/views/user_notifications/digest.html.erb b/app/views/user_notifications/digest.html.erb
index 9cd96523049..9c7c64d3f2b 100644
--- a/app/views/user_notifications/digest.html.erb
+++ b/app/views/user_notifications/digest.html.erb
@@ -70,7 +70,7 @@
   <span class='footer-notice'>
     <%=raw(t :'user_notifications.digest.unsubscribe',
        site_link: html_site_link,
-       unsubscribe_link: link_to(t('user_notifications.digest.click_here'), email_unsubscribe_path(host: Discourse.base_url, key: @user.temporary_key, only_path: false)))  %>
+       unsubscribe_link: link_to(t('user_notifications.digest.click_here'), email_unsubscribe_url(host: Discourse.base_url, key: @user.temporary_key)))  %>
   </span>
   </td>
 </tr>
diff --git a/app/views/user_notifications/digest.text.erb b/app/views/user_notifications/digest.text.erb
index b0735a373a7..8c86148aafc 100644
--- a/app/views/user_notifications/digest.text.erb
+++ b/app/views/user_notifications/digest.text.erb
@@ -33,7 +33,6 @@
 
 <%=raw(t :'user_notifications.digest.unsubscribe',
      site_link: site_link,
-     unsubscribe_link: raw(@markdown_linker.create(t('user_notifications.digest.click_here'), email_unsubscribe_path(key: @user.temporary_key))))  %>
+     unsubscribe_link: raw(@markdown_linker.create(t('user_notifications.digest.click_here'), email_unsubscribe_url(key: @user.temporary_key, only_path: true))))  %>
 
 <%= raw(@markdown_linker.references) %>
-
diff --git a/config/application.rb b/config/application.rb
index 3e0010aef71..acc2d501733 100644
--- a/config/application.rb
+++ b/config/application.rb
@@ -110,6 +110,11 @@ module Discourse
     # see: http://stackoverflow.com/questions/11894180/how-does-one-correctly-add-custom-sql-dml-in-migrations/11894420#11894420
     config.active_record.schema_format = :sql
 
+    if rails_master?
+      # Opt-into the default behavior in Rails 5
+      # config.active_record.raise_in_transactional_callbacks = true
+    end
+
     # per https://www.owasp.org/index.php/Password_Storage_Cheat_Sheet
     config.pbkdf2_iterations = 64000
     config.pbkdf2_algorithm = "sha256"
diff --git a/config/initializers/00-rails-master-polyfills.rb b/config/initializers/00-rails-master-polyfills.rb
new file mode 100644
index 00000000000..c32131a9ae9
--- /dev/null
+++ b/config/initializers/00-rails-master-polyfills.rb
@@ -0,0 +1,8 @@
+unless rails_master?
+
+class Mail::Message
+  alias_method :deliver_now,  :deliver
+  alias_method :deliver_now!, :deliver!
+end
+
+end
diff --git a/lib/email/sender.rb b/lib/email/sender.rb
index bc16b2bf98c..8fcbd1c5f14 100644
--- a/lib/email/sender.rb
+++ b/lib/email/sender.rb
@@ -115,7 +115,7 @@ module Email
       end
 
       begin
-        @message.deliver
+        @message.deliver_now
       rescue *SMTP_CLIENT_ERRORS => e
         return skip(e.message)
       end
diff --git a/lib/freedom_patches/pool_drainer.rb b/lib/freedom_patches/pool_drainer.rb
index f953b32a42d..f6e2498a530 100644
--- a/lib/freedom_patches/pool_drainer.rb
+++ b/lib/freedom_patches/pool_drainer.rb
@@ -1,6 +1,29 @@
 
+if rails_master?
+  class ActiveRecord::ConnectionAdapters::AbstractAdapter
+    module LastUseExtension
+      attr_reader :last_use
+
+      def initialize(connection, logger = nil, pool = nil)
+        super
+        @last_use = false
+      end
+
+      def lease
+        synchronize do
+          unless in_use?
+            @last_use = Time.now
+            super
+          end
+        end
+      end
+    end
+
+    prepend LastUseExtension
+  end
+end
+
 class ActiveRecord::ConnectionAdapters::ConnectionPool
-
   # drain all idle connections
   # if idle_time is specified only connections idle for N seconds will be drained
   def drain(idle_time=nil)
@@ -29,5 +52,4 @@ class ActiveRecord::ConnectionAdapters::ConnectionPool
 
     false
   end
-
 end
diff --git a/lib/sass/discourse_sass_compiler.rb b/lib/sass/discourse_sass_compiler.rb
index ec8d729fc28..ebb799ecc8d 100644
--- a/lib/sass/discourse_sass_compiler.rb
+++ b/lib/sass/discourse_sass_compiler.rb
@@ -1,4 +1,5 @@
 require_dependency 'sass/discourse_sass_importer'
+require 'pathname'
 
 class DiscourseSassCompiler
 
@@ -41,7 +42,8 @@ class DiscourseSassCompiler
       env = env.instance_variable_get('@environment')
     end
 
-    context = env.context_class.new(env, "#{@target}.scss", "app/assets/stylesheets/#{@target}.scss")
+    pathname = Pathname.new("app/assets/stylesheets/#{@target}.scss")
+    context = env.context_class.new(env, "#{@target}.scss", pathname)
 
     debug_opts = Rails.env.production? ? {} : {
       line_numbers: true,
diff --git a/lib/sql_builder.rb b/lib/sql_builder.rb
index 5a99f27718c..6521afeb020 100644
--- a/lib/sql_builder.rb
+++ b/lib/sql_builder.rb
@@ -71,11 +71,20 @@ class SqlBuilder
 
   #AS reloads this on tests
   remove_const :FTYPE_MAP if defined? FTYPE_MAP
-  FTYPE_MAP = {
-    23 => :value_to_integer,
-    1114 => :string_to_time,
-    16 => :value_to_boolean
-  }
+
+  if rails_master?
+    FTYPE_MAP = {
+      23 => ActiveRecord::Type::Integer.new,
+      1114 => ActiveRecord::Type::DateTime.new,
+      16 => ActiveRecord::Type::Boolean.new
+    }
+  else
+    FTYPE_MAP = {
+      23 => :value_to_integer,
+      1114 => :string_to_time,
+      16 => :value_to_boolean
+    }
+  end
 
   def self.map_exec(klass, sql, args = {})
     self.new(sql).map_exec(klass, args)
@@ -93,7 +102,11 @@ class SqlBuilder
       setters.each_with_index do |mapper, index|
         translated = row[index]
         if mapper[1] && !translated.nil?
-          translated = ActiveRecord::ConnectionAdapters::Column.send mapper[1], translated
+          if rails_master?
+            translated = mapper[1].type_cast_from_database(translated)
+          else
+            translated = ActiveRecord::ConnectionAdapters::Column.send mapper[1], translated
+          end
         end
         mapped.send mapper[0], translated
       end
diff --git a/script/test_email_settings.rb b/script/test_email_settings.rb
index fe7fdb54d27..dc8422edd60 100644
--- a/script/test_email_settings.rb
+++ b/script/test_email_settings.rb
@@ -38,7 +38,7 @@ end
 message = EmailTestMailer.email_test(MAILFROM, MAILTO)
 
 begin
-  message.deliver()
+  message.deliver_now()
 rescue SocketError => e
   print "Delivery failed: "+e.message.strip()+"\n"
   print " Is the server hostname correct?\n"
diff --git a/spec/components/email/sender_spec.rb b/spec/components/email/sender_spec.rb
index 3853f82ca15..f3b027d8ef8 100644
--- a/spec/components/email/sender_spec.rb
+++ b/spec/components/email/sender_spec.rb
@@ -5,25 +5,25 @@ describe Email::Sender do
 
   it "doesn't deliver mail when mails are disabled" do
     SiteSetting.expects(:disable_emails).returns(true)
-    Mail::Message.any_instance.expects(:deliver).never
+    Mail::Message.any_instance.expects(:deliver_now).never
     message = Mail::Message.new(to: "hello@world.com" , body: "hello")
     Email::Sender.new(message, :hello).send
   end
 
   it "doesn't deliver mail when the message is nil" do
-    Mail::Message.any_instance.expects(:deliver).never
+    Mail::Message.any_instance.expects(:deliver_now).never
     Email::Sender.new(nil, :hello).send
   end
 
   it "doesn't deliver when the to address is nil" do
     message = Mail::Message.new(body: 'hello')
-    message.expects(:deliver).never
+    message.expects(:deliver_now).never
     Email::Sender.new(message, :hello).send
   end
 
   it "doesn't deliver when the body is nil" do
     message = Mail::Message.new(to: 'eviltrout@test.domain')
-    message.expects(:deliver).never
+    message.expects(:deliver_now).never
     Email::Sender.new(message, :hello).send
   end
 
@@ -53,14 +53,14 @@ describe Email::Sender do
     let(:message) do
       message = Mail::Message.new to: 'eviltrout@test.domain',
                                   body: '**hello**'
-      message.stubs(:deliver)
+      message.stubs(:deliver_now)
       message
     end
 
     let(:email_sender) { Email::Sender.new(message, :valid_type) }
 
     it 'calls deliver' do
-      message.expects(:deliver).once
+      message.expects(:deliver_now).once
       email_sender.send
     end
 
@@ -131,7 +131,7 @@ describe Email::Sender do
   context 'with a user' do
     let(:message) do
       message = Mail::Message.new to: 'eviltrout@test.domain', body: 'test body'
-      message.stubs(:deliver)
+      message.stubs(:deliver_now)
       message
     end
 
diff --git a/spec/mailers/user_notifications_spec.rb b/spec/mailers/user_notifications_spec.rb
index cdde34812ed..a8ddc4246df 100644
--- a/spec/mailers/user_notifications_spec.rb
+++ b/spec/mailers/user_notifications_spec.rb
@@ -112,14 +112,21 @@ describe UserNotifications do
       # in mailing list mode user_replies is not sent through
       response.user.mailing_list_mode = true
       mail = UserNotifications.user_replied(response.user, post: response, notification: notification)
-      mail.class.should == ActionMailer::Base::NullMail
 
+      if rails_master?
+        mail.message.class.should == ActionMailer::Base::NullMail
+      else
+        mail.class.should == ActionMailer::Base::NullMail
+      end
 
       response.user.mailing_list_mode = nil
       mail = UserNotifications.user_replied(response.user, post: response, notification: notification)
 
-      mail.class.should_not == ActionMailer::Base::NullMail
-
+      if rails_master?
+        mail.message.class.should_not == ActionMailer::Base::NullMail
+      else
+        mail.class.should_not == ActionMailer::Base::NullMail
+      end
     end
   end
 
@@ -183,7 +190,16 @@ describe UserNotifications do
 
   def expects_build_with(condition)
     UserNotifications.any_instance.expects(:build_email).with(user.email, condition)
-    UserNotifications.send(mail_type, user, notification: notification, post: notification.post)
+    mailer = UserNotifications.send(mail_type, user, notification: notification, post: notification.post)
+
+    if rails_master?
+      # Starting from Rails 4.2, calling MyMailer.some_method no longer result
+      # in an immediate call to MyMailer#some_method. Instead, a "lazy proxy" is
+      # returned (this is changed to support #deliver_later). As a quick hack to
+      # fix the test, calling #message (or anything, really) would force the
+      # Mailer object to be created and the method invoked.
+      mailer.message
+    end
   end
 
   shared_examples "supports reply by email" do