diff --git a/.rubocop.yml b/.rubocop.yml
index df79935..358d924 100644
--- a/.rubocop.yml
+++ b/.rubocop.yml
@@ -25,21 +25,24 @@ Style/SignalException:
 Style/RaiseArgs:
   Enabled: false
 
-Layout/AlignParameters:
+Layout/ParameterAlignment:
   EnforcedStyle: with_fixed_indentation
 
-Layout/AlignHash:
+Layout/HashAlignment:
   Enabled: false
 
-Layout/AlignArray:
+Layout/ArrayAlignment:
   Enabled: false
 
 Layout/MultilineOperationIndentation:
   EnforcedStyle: indented
 
-Layout/IndentFirstHashElement:
+Layout/FirstHashElementIndentation:
   EnforcedStyle: consistent
 
+Layout/SpaceAroundMethodCallOperator:
+  Enabled: true
+
 Style/Documentation:
   Enabled: false
 
@@ -50,6 +53,24 @@ Style/BlockDelimiters:
 Style/ModuleFunction:
   Enabled: false
 
+Style/ExponentialNotation:
+  Enabled: true
+
+Style/HashEachMethods:
+  Enabled: true
+
+Style/HashTransformKeys:
+  Enabled: true
+
+Style/HashTransformValues:
+  Enabled: true
+
 Lint/RescueException:
   Exclude:
     - 'lib/health_monitor/providers/**/*'
+
+Lint/RaiseException:
+  Enabled: true
+
+Lint/StructNewOverride:
+  Enabled: true
diff --git a/.travis.yml b/.travis.yml
index 49320db..1f07ff9 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,9 +1,8 @@
 language: ruby
 rvm:
-  - 2.3.8
-  - 2.4.5
-  - 2.5.3
-  - 2.6.2
+  - 2.5.8
+  - 2.6.6
+  - 2.7.0
   - ruby-head
 gemfile:
   - gemfiles/rails_5.0.gemfile
@@ -12,16 +11,8 @@ gemfile:
   - gemfiles/rails_6.0.gemfile
 matrix:
   exclude:
-    - rvm: 2.3.8
-      gemfile: gemfiles/rails_6.0.gemfile
-    - rvm: 2.4.5
-      gemfile: gemfiles/rails_6.0.gemfile
     - rvm: ruby-head
       gemfile: gemfiles/rails_5.0.gemfile
-    - rvm: ruby-head
-      gemfile: gemfiles/rails_5.1.gemfile
-    - rvm: ruby-head
-      gemfile: gemfiles/rails_5.2.gemfile
 script:
   - bundle exec rake rubocop
   - bundle exec rspec
diff --git a/Appraisals b/Appraisals
index 832c605..0670d2d 100644
--- a/Appraisals
+++ b/Appraisals
@@ -1,17 +1,17 @@
 # frozen_string_literal: true
 
 appraise 'rails-5.0' do
-  gem 'rails', '~> 5.0.7.1'
+  gem 'rails', '~> 5.0.7.2'
 end
 
 appraise 'rails-5.1' do
-  gem 'rails', '~> 5.1.6.1'
+  gem 'rails', '~> 5.1.6.2'
 end
 
 appraise 'rails-5.2' do
-  gem 'rails', '~> 5.2.2'
+  gem 'rails', '~> 5.2.4.2'
 end
 
 appraise 'rails-6.0' do
-  gem 'rails', '~> 6.0.0'
+  gem 'rails', '~> 6.0.2.2'
 end
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 05726cd..ac76c11 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,9 @@
 # Changelog
 
+## 8.9.0 (2020-04-16)
+
+- Deprecate Ruby 2.4.0 and update dependencies and style.
+
 ## 8.8.0 (2019-11-12)
 
 - Replace dependency for rails with railties (thanks to @sliiser).
diff --git a/gemfiles/rails_5.0.gemfile b/gemfiles/rails_5.0.gemfile
index 0687f30..19badf2 100644
--- a/gemfiles/rails_5.0.gemfile
+++ b/gemfiles/rails_5.0.gemfile
@@ -4,7 +4,7 @@
 
 source 'https://rubygems.org'
 
-gem 'railties', '~> 5.0.7.1'
+gem 'rails', '~> 5.0.7.2'
 gem 'sqlite3', '~> 1.3.6'
 
 gemspec path: '../'
diff --git a/gemfiles/rails_5.1.gemfile b/gemfiles/rails_5.1.gemfile
index 6cd588d..f040cc9 100644
--- a/gemfiles/rails_5.1.gemfile
+++ b/gemfiles/rails_5.1.gemfile
@@ -4,7 +4,7 @@
 
 source 'https://rubygems.org'
 
-gem 'railties', '~> 5.1.6.1'
+gem 'rails', '~> 5.1.6.2'
 gem 'sqlite3', '~> 1.3.6'
 
 gemspec path: '../'
diff --git a/gemfiles/rails_5.2.gemfile b/gemfiles/rails_5.2.gemfile
index 6eafe81..9561ea3 100644
--- a/gemfiles/rails_5.2.gemfile
+++ b/gemfiles/rails_5.2.gemfile
@@ -4,6 +4,7 @@
 
 source 'https://rubygems.org'
 
-gem 'railties', '~> 5.2.2'
+gem 'rails', '~> 5.2.4.2'
+gem 'sqlite3', '~> 1.4'
 
 gemspec path: '../'
diff --git a/gemfiles/rails_6.0.gemfile b/gemfiles/rails_6.0.gemfile
index 714da28..d2baf43 100644
--- a/gemfiles/rails_6.0.gemfile
+++ b/gemfiles/rails_6.0.gemfile
@@ -4,6 +4,7 @@
 
 source 'https://rubygems.org'
 
-gem 'railties', '~> 6.0.0'
+gem 'rails', '~> 6.0.2.2'
+gem 'sqlite3', '~> 1.4'
 
 gemspec path: '../'
diff --git a/lib/health_monitor/version.rb b/lib/health_monitor/version.rb
index 12ef0c8..42f57ae 100644
--- a/lib/health_monitor/version.rb
+++ b/lib/health_monitor/version.rb
@@ -1,5 +1,5 @@
 # frozen_string_literal: true
 
 module HealthMonitor
-  VERSION = '8.8.0'
+  VERSION = '8.9.0'
 end
diff --git a/spec/dummy/app/assets/config/manifest.js b/spec/dummy/app/assets/config/manifest.js
new file mode 100644
index 0000000..b16e53d
--- /dev/null
+++ b/spec/dummy/app/assets/config/manifest.js
@@ -0,0 +1,3 @@
+//= link_tree ../images
+//= link_directory ../javascripts .js
+//= link_directory ../stylesheets .css
diff --git a/spec/spec_helper.rb b/spec/spec_helper.rb
index 5885e3b..a71237d 100644
--- a/spec/spec_helper.rb
+++ b/spec/spec_helper.rb
@@ -16,8 +16,8 @@
   require 'pry'
   require 'rediska'
 
-  Dir[File.expand_path('../lib/**/*.rb', __dir__)].each { |f| require f }
-  Dir[File.expand_path('support/**/*.rb', __dir__)].each { |f| require f }
+  Dir[File.expand_path('../lib/**/*.rb', __dir__)].sort.each { |f| require f }
+  Dir[File.expand_path('support/**/*.rb', __dir__)].sort.each { |f| require f }
 
   RSpec.configure do |config|
     config.mock_with :rspec
diff --git a/spec/support/providers.rb b/spec/support/providers.rb
index dafe865..d10a311 100644
--- a/spec/support/providers.rb
+++ b/spec/support/providers.rb
@@ -1,6 +1,7 @@
 # frozen_string_literal: true
 
 require 'spec_helper'
+require 'rspec/mocks'
 
 module Providers
   include RSpec::Mocks::ExampleMethods