diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
new file mode 100644
index 00000000..c7d01e20
--- /dev/null
+++ b/.github/workflows/test.yml
@@ -0,0 +1,80 @@
+name: CI Tests
+
+on:
+  push:
+    branches: [master]
+  pull_request:
+    branches: ['**']
+
+jobs:
+  test:
+    services:
+      postgres:
+        image: postgres
+        env:
+          POSTGRES_DB: i18n_unittest
+          POSTGRES_PASSWORD: postgres
+        ports:
+          - 5432:5432
+        options: >-
+          --health-cmd pg_isready
+          --health-interval 10s
+          --health-timeout 5s
+          --health-retries 5
+      mysql:
+        image: mysql:5.7
+        env:
+          MYSQL_DATABASE: i18n_unittest
+          MYSQL_ALLOW_EMPTY_PASSWORD: true
+        ports:
+          - '3306:3306'
+        options: >-
+          --health-cmd="mysqladmin ping"
+          --health-interval=10s
+          --health-timeout=5s
+          --health-retries=3
+    strategy:
+      fail-fast: true
+      matrix:
+        ruby: [2.4, 2.5, 2.6, 2.7, 3.0, 'head']
+        rails: [4, 5, 6, 'head']
+        exclude:
+          - ruby: 2.4
+            rails: 6
+          - ruby: 2.4
+            rails: head
+          - ruby: 2.5
+            rails: head
+          - ruby: 2.6
+            rails: head
+          - ruby: 2.7
+            rails: 4
+          - ruby: 3.0
+            rails: 4
+          - ruby: 3.0
+            rails: 5
+          - ruby: head
+            rails: 4
+          - ruby: head
+            rails: 5
+    name: 'Ruby: ${{ matrix.ruby }}, Rails: ${{ matrix.rails }}'
+    runs-on: ubuntu-latest
+    env:
+      BUNDLE_GEMFILE: ${{ github.workspace }}/gemfiles/Gemfile.rails_${{ matrix.rails }}
+    steps:
+      - uses: actions/checkout@v2
+      - uses: ruby/setup-ruby@v1
+        with:
+          ruby-version: ${{ matrix.ruby }}
+          bundler-cache: true
+          cache-version: 1
+      - name: Run tests for SQLite
+        run: bundle exec rake
+      - name: Run tests for PostgreSQL
+        env:
+          DB: postgres
+        run: bundle exec rake
+      - name: Run tests for MySQL
+        env:
+          DB: mysql
+        run: bundle exec rake
diff --git a/.travis.yml b/.travis.yml
deleted file mode 100644
index f6308e71..00000000
--- a/.travis.yml
+++ /dev/null
@@ -1,49 +0,0 @@
-language: ruby
-cache: bundler
-
-notifications:
-  email: false
-
-services:
-  - postgresql
-  - mysql
-
-before_install:
-  - gem install bundler -v 2.0.2
-
-before_script:
-  - mysql -e 'create database i18n_unittest;'
-  - psql -c 'create database i18n_unittest;' -U postgres
-
-rvm:
-  - 2.3
-  - 2.4
-  - 2.5
-  - 2.6
-  - 2.7
-
-gemfile:
-  - gemfiles/Gemfile.rails_3
-  - gemfiles/Gemfile.rails_4
-  - gemfiles/Gemfile.rails_5
-  - gemfiles/Gemfile.rails_6
-  - gemfiles/Gemfile.rails_head
-
-env:
-  - PG_USER=postgres
-
-matrix:
-  fast_finish: true
-  exclude:
-    - rvm: 2.3
-      gemfile: gemfiles/Gemfile.rails_6
-    - rvm: 2.4
-      gemfile: gemfiles/Gemfile.rails_6
-    - rvm: 2.3
-      gemfile: gemfiles/Gemfile.rails_head
-    - rvm: 2.4
-      gemfile: gemfiles/Gemfile.rails_head
-    - rvm: 2.5
-      gemfile: gemfiles/Gemfile.rails_head
-    - rvm: 2.6
-      gemfile: gemfiles/Gemfile.rails_head
diff --git a/Gemfile.lock b/Gemfile.lock
index 8990895c..482fc350 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -1,7 +1,7 @@
 PATH
   remote: .
   specs:
-    i18n-active_record (0.4.0)
+    i18n-active_record (0.4.1)
       i18n (>= 0.5.0)
 
 GEM
@@ -22,12 +22,12 @@ GEM
     i18n (1.8.10)
       concurrent-ruby (~> 1.0)
     minitest (5.14.4)
-    mocha (1.12.0)
+    mocha (1.13.0)
     mysql2 (0.5.3)
     pg (1.2.3)
-    rake (13.0.3)
+    rake (13.0.1)
     sqlite3 (1.4.2)
-    test_declarative (0.0.6)
+    test_declarative (0.0.5)
     tzinfo (2.0.4)
       concurrent-ruby (~> 1.0)
     zeitwerk (2.4.2)
@@ -48,4 +48,4 @@ DEPENDENCIES
   test_declarative
 
 BUNDLED WITH
-   2.1.4
+   2.2.29
diff --git a/README.md b/README.md
index a1f65061..96f6b887 100644
--- a/README.md
+++ b/README.md
@@ -1,7 +1,7 @@
-# I18n::Backend::ActiveRecord
+# I18n::Backend::ActiveRecord ![Build Status](https://github.com/svenfuchs/i18n-active_record/actions/workflows/test.yml/badge.svg)
 
 This repository contains the I18n ActiveRecord backend and support code that has been extracted from the "I18n": http://github.com/svenfuchs/i18n.
-It is fully compatible with Rails 3, 4, 5 and 6.
+It is fully compatible with Rails 4, 5 and 6.
 
 ## Installation
 
@@ -77,11 +77,37 @@ I18n::Backend::ActiveRecord.configure do |config|
 end
 ```
 
+To configure the ActiveRecord backend to cache translations(might be useful in production) use:
+
+```ruby
+I18n::Backend::ActiveRecord.configure do |config|
+  config.cache_translations = true # defaults to false
+end
+```
+
 ## Usage
 
 You can now use `I18n.t('Your String')` to lookup translations in the database.
 
-## Missing Translations -> Interpolations
+## Missing Translations
+
+### Usage
+
+In order to make the `I18n::Backend::ActiveRecord::Missing` module working correctly pluralization rules should be configured properly.
+The `i18n.plural.keys` translation key should be present in any of the backends.
+(See https://github.com/svenfuchs/i18n-active_record/blob/master/lib/i18n/backend/active_record/missing.rb for more information)
+
+```yaml
+en:
+  i18n:
+    plural:
+      keys:
+        - :zero
+        - :one
+        - :other
+```
+
+### Interpolations
 
 The `interpolations` field in the `translations` table is used by `I18n::Backend::ActiveRecord::Missing` to store the interpolations seen the first time this Translation was requested.  This will help translators understand what interpolations to expect, and thus to include when providing the translations.
 
@@ -93,7 +119,20 @@ The `interpolations` field is otherwise unused since the "value" in `Translation
 
 ## Contributing
 
-To run the test suite for all databases use `rake test` or using only SQLite with `rake sqlite:test`
+### Test suite
+
+The test suite can be run with:
+
+    bundle exec rake
+
+By default it runs the tests for SQLite database, to specify a database the `DB` env variable can be used:
+
+    DB=postgres bundle exec rake
+    DB=mysql bundle exec rake
+
+There are multiple gemfiles(mostly used for CI) and they can be activated with the `--gemfile` option:
+
+    bundle exec --gemfile gemfiles/Gemfile.rails_4 rake
 
 ## Maintainers
 
diff --git a/Rakefile b/Rakefile
index f8923285..4f45d1cc 100644
--- a/Rakefile
+++ b/Rakefile
@@ -1,66 +1,9 @@
-require 'rake'
 require 'rake/testtask'
-require 'bundler/gem_tasks'
 
-def execute(command)
-  puts command
-  system command
-end
-
-def bundle_options
-  return '' unless ENV['BUNDLE_GEMFILE']
-
-  "--gemfile #{ENV['BUNDLE_GEMFILE']}"
-end
-
-def each_database(&block)
-  ['sqlite', 'postgres', 'mysql'].each &block
-end
-
-namespace :bundle do
-  task :env do
-    ar = ENV['AR'].to_s
-
-    next if ar.empty?
-
-    gemfile = "gemfiles/Gemfile.rails_#{ar}"
-    raise "Cannot find gemfile at #{gemfile}" unless File.exist?(gemfile)
-
-    ENV['BUNDLE_GEMFILE'] = gemfile
-    puts "Using gemfile: #{gemfile}"
-  end
-
-  task install: :env do
-    execute "bundle install #{bundle_options}"
-  end
-
-  task update: :env do
-    execute "bundle update #{bundle_options}"
-  end
-
-  task :install_all do
-    [nil, '3', '4', '5', '6', 'head'].each do |ar|
-      opt = ar && "AR=#{ar}"
-      execute "rake bundle:install #{opt}"
-    end
-  end
-end
-
-task :test do
-  each_database { |db| execute "rake #{db}:test" }
-end
-
-Rake::TestTask.new :_test do |t|
+Rake::TestTask.new :test do |t|
   t.libs << 'test'
   t.pattern = 'test/**/*_test.rb'
   t.verbose = false
 end
 
-each_database do |db|
-  namespace db do
-    task(:env) { ENV['DB'] = db }
-    task test: ['env', 'bundle:env', '_test']
-  end
-end
-
 task default: :test
diff --git a/gemfiles/Gemfile.rails_3 b/gemfiles/Gemfile.rails_3
deleted file mode 100644
index fbb82cfc..00000000
--- a/gemfiles/Gemfile.rails_3
+++ /dev/null
@@ -1,13 +0,0 @@
-source 'https://rubygems.org'
-
-gemspec path: '..'
-
-gem 'activerecord', '~> 3.2.0'
-gem 'sqlite3'
-gem 'mysql2'
-gem 'pg', '~> 0.18.0'
-
-gem 'minitest'
-gem 'test_declarative'
-gem 'mocha'
-gem 'rake'
diff --git a/gemfiles/Gemfile.rails_3.lock b/gemfiles/Gemfile.rails_3.lock
deleted file mode 100644
index ce2906cd..00000000
--- a/gemfiles/Gemfile.rails_3.lock
+++ /dev/null
@@ -1,52 +0,0 @@
-PATH
-  remote: ..
-  specs:
-    i18n-active_record (0.4.0)
-      i18n (>= 0.5.0)
-
-GEM
-  remote: https://rubygems.org/
-  specs:
-    activemodel (3.2.22.5)
-      activesupport (= 3.2.22.5)
-      builder (~> 3.0.0)
-    activerecord (3.2.22.5)
-      activemodel (= 3.2.22.5)
-      activesupport (= 3.2.22.5)
-      arel (~> 3.0.2)
-      tzinfo (~> 0.3.29)
-    activesupport (3.2.22.5)
-      i18n (~> 0.6, >= 0.6.4)
-      multi_json (~> 1.0)
-    arel (3.0.3)
-    builder (3.0.4)
-    i18n (0.8.1)
-    metaclass (0.0.4)
-    minitest (5.10.1)
-    mocha (1.2.1)
-      metaclass (~> 0.0.1)
-    multi_json (1.12.1)
-    mysql2 (0.4.5)
-    pg (0.18.4)
-    rake (13.0.1)
-    sqlite3 (1.3.13)
-    test_declarative (0.0.5)
-    tzinfo (0.3.52)
-
-PLATFORMS
-  ruby
-
-DEPENDENCIES
-  activerecord (~> 3.2.0)
-  bundler
-  i18n-active_record!
-  minitest
-  mocha
-  mysql2
-  pg (~> 0.18.0)
-  rake
-  sqlite3
-  test_declarative
-
-BUNDLED WITH
-   2.0.2
diff --git a/gemfiles/Gemfile.rails_4.lock b/gemfiles/Gemfile.rails_4.lock
index 348a0081..00d7f045 100644
--- a/gemfiles/Gemfile.rails_4.lock
+++ b/gemfiles/Gemfile.rails_4.lock
@@ -1,7 +1,7 @@
 PATH
   remote: ..
   specs:
-    i18n-active_record (0.4.0)
+    i18n-active_record (0.4.1)
       i18n (>= 0.5.0)
 
 GEM
@@ -22,11 +22,9 @@ GEM
     arel (6.0.4)
     builder (3.2.3)
     i18n (0.8.1)
-    metaclass (0.0.4)
     minitest (5.10.1)
-    mocha (1.2.1)
-      metaclass (~> 0.0.1)
-    mysql2 (0.4.5)
+    mocha (1.13.0)
+    mysql2 (0.4.10)
     pg (0.18.4)
     rake (13.0.1)
     sqlite3 (1.3.13)
diff --git a/gemfiles/Gemfile.rails_5.lock b/gemfiles/Gemfile.rails_5.lock
index 189dfa1c..2a99ed44 100644
--- a/gemfiles/Gemfile.rails_5.lock
+++ b/gemfiles/Gemfile.rails_5.lock
@@ -1,32 +1,32 @@
 PATH
   remote: ..
   specs:
-    i18n-active_record (0.4.0)
+    i18n-active_record (0.4.1)
       i18n (>= 0.5.0)
 
 GEM
   remote: https://rubygems.org/
   specs:
-    activemodel (5.2.4.5)
-      activesupport (= 5.2.4.5)
-    activerecord (5.2.4.5)
-      activemodel (= 5.2.4.5)
-      activesupport (= 5.2.4.5)
+    activemodel (5.2.6)
+      activesupport (= 5.2.6)
+    activerecord (5.2.6)
+      activemodel (= 5.2.6)
+      activesupport (= 5.2.6)
       arel (>= 9.0)
-    activesupport (5.2.4.5)
+    activesupport (5.2.6)
       concurrent-ruby (~> 1.0, >= 1.0.2)
       i18n (>= 0.7, < 2)
       minitest (~> 5.1)
       tzinfo (~> 1.1)
     arel (9.0.0)
-    concurrent-ruby (1.1.8)
-    i18n (1.8.9)
+    concurrent-ruby (1.1.9)
+    i18n (1.8.10)
       concurrent-ruby (~> 1.0)
     minitest (5.14.4)
-    mocha (1.12.0)
+    mocha (1.13.0)
     mysql2 (0.5.3)
     pg (1.2.3)
-    rake (13.0.3)
+    rake (13.0.6)
     sqlite3 (1.4.2)
     test_declarative (0.0.6)
     thread_safe (0.3.6)
@@ -49,4 +49,4 @@ DEPENDENCIES
   test_declarative
 
 BUNDLED WITH
-   2.1.4
+   2.2.16
diff --git a/gemfiles/Gemfile.rails_6.lock b/gemfiles/Gemfile.rails_6.lock
index 7b6c249a..0ba96ee4 100644
--- a/gemfiles/Gemfile.rails_6.lock
+++ b/gemfiles/Gemfile.rails_6.lock
@@ -1,36 +1,36 @@
 PATH
   remote: ..
   specs:
-    i18n-active_record (0.4.0)
+    i18n-active_record (0.4.1)
       i18n (>= 0.5.0)
 
 GEM
   remote: https://rubygems.org/
   specs:
-    activemodel (6.1.3)
-      activesupport (= 6.1.3)
-    activerecord (6.1.3)
-      activemodel (= 6.1.3)
-      activesupport (= 6.1.3)
-    activesupport (6.1.3)
+    activemodel (6.1.4.1)
+      activesupport (= 6.1.4.1)
+    activerecord (6.1.4.1)
+      activemodel (= 6.1.4.1)
+      activesupport (= 6.1.4.1)
+    activesupport (6.1.4.1)
       concurrent-ruby (~> 1.0, >= 1.0.2)
       i18n (>= 1.6, < 2)
       minitest (>= 5.1)
       tzinfo (~> 2.0)
       zeitwerk (~> 2.3)
-    concurrent-ruby (1.1.8)
-    i18n (1.8.9)
+    concurrent-ruby (1.1.9)
+    i18n (1.8.10)
       concurrent-ruby (~> 1.0)
     minitest (5.14.4)
-    mocha (1.12.0)
+    mocha (1.13.0)
     mysql2 (0.5.3)
     pg (1.2.3)
-    rake (13.0.3)
+    rake (13.0.6)
     sqlite3 (1.4.2)
     test_declarative (0.0.6)
     tzinfo (2.0.4)
       concurrent-ruby (~> 1.0)
-    zeitwerk (2.4.2)
+    zeitwerk (2.5.1)
 
 PLATFORMS
   ruby
@@ -48,4 +48,4 @@ DEPENDENCIES
   test_declarative
 
 BUNDLED WITH
-   2.1.4
+   2.2.16
diff --git a/gemfiles/Gemfile.rails_head.lock b/gemfiles/Gemfile.rails_head.lock
index c698fac9..2f154b3e 100644
--- a/gemfiles/Gemfile.rails_head.lock
+++ b/gemfiles/Gemfile.rails_head.lock
@@ -1,42 +1,40 @@
 GIT
   remote: https://github.com/rails/rails
-  revision: a8c462d37c1e482fa0a0fc16014fc9ad1d97032f
+  revision: 2451a568aff34816f1df7bd92b158fb059771337
   branch: main
   specs:
-    activemodel (7.0.0.alpha)
-      activesupport (= 7.0.0.alpha)
-    activerecord (7.0.0.alpha)
-      activemodel (= 7.0.0.alpha)
-      activesupport (= 7.0.0.alpha)
-    activesupport (7.0.0.alpha)
+    activemodel (7.0.0.alpha2)
+      activesupport (= 7.0.0.alpha2)
+    activerecord (7.0.0.alpha2)
+      activemodel (= 7.0.0.alpha2)
+      activesupport (= 7.0.0.alpha2)
+    activesupport (7.0.0.alpha2)
       concurrent-ruby (~> 1.0, >= 1.0.2)
       i18n (>= 1.6, < 2)
       minitest (>= 5.1)
       tzinfo (~> 2.0)
-      zeitwerk (~> 2.3)
 
 PATH
   remote: ..
   specs:
-    i18n-active_record (0.4.0)
+    i18n-active_record (0.4.1)
       i18n (>= 0.5.0)
 
 GEM
   remote: https://rubygems.org/
   specs:
-    concurrent-ruby (1.1.8)
-    i18n (1.8.9)
+    concurrent-ruby (1.1.9)
+    i18n (1.8.10)
       concurrent-ruby (~> 1.0)
     minitest (5.14.4)
-    mocha (1.12.0)
+    mocha (1.13.0)
     mysql2 (0.5.3)
     pg (1.2.3)
-    rake (13.0.3)
+    rake (13.0.6)
     sqlite3 (1.4.2)
     test_declarative (0.0.6)
     tzinfo (2.0.4)
       concurrent-ruby (~> 1.0)
-    zeitwerk (2.4.2)
 
 PLATFORMS
   ruby
@@ -54,4 +52,4 @@ DEPENDENCIES
   test_declarative
 
 BUNDLED WITH
-   2.1.4
+   2.2.16
diff --git a/lib/i18n/backend/active_record.rb b/lib/i18n/backend/active_record.rb
index 15e5042c..58a4489d 100644
--- a/lib/i18n/backend/active_record.rb
+++ b/lib/i18n/backend/active_record.rb
@@ -9,6 +9,9 @@ class ActiveRecord
       autoload :Translation,   'i18n/backend/active_record/translation'
       autoload :Configuration, 'i18n/backend/active_record/configuration'
 
+      include Base
+      include Flatten
+
       class << self
         def configure
           yield(config) if block_given?
@@ -19,114 +22,111 @@ def config
         end
       end
 
-      module Implementation
-        include Base, Flatten
+      def initialize(*args)
+        super
 
-        def available_locales
-          begin
-            Translation.available_locales
-          rescue ::ActiveRecord::StatementInvalid
-            []
-          end
-        end
+        reload!
+      end
 
-        def store_translations(locale, data, options = {})
-          escape = options.fetch(:escape, true)
-          flatten_translations(locale, data, escape, false).each do |key, value|
-            translation = Translation.locale(locale).lookup(expand_keys(key))
+      def available_locales
+        Translation.available_locales
+      rescue ::ActiveRecord::StatementInvalid
+        []
+      end
 
-            if ActiveRecord.config.cleanup_with_destroy
-              translation.destroy_all
-            else
-              translation.delete_all
-            end
+      def store_translations(locale, data, options = {})
+        escape = options.fetch(:escape, true)
 
-            Translation.create(:locale => locale.to_s, :key => key.to_s, :value => value)
+        flatten_translations(locale, data, escape, false).each do |key, value|
+          translation = Translation.locale(locale).lookup(expand_keys(key))
+
+          if ActiveRecord.config.cleanup_with_destroy
+            translation.destroy_all
+          else
+            translation.delete_all
           end
 
-          reload! if ActiveRecord.config.cache_translations
+          Translation.create(locale: locale.to_s, key: key.to_s, value: value)
         end
 
-        def reload!
-          @translations = nil
+        reload! if ActiveRecord.config.cache_translations
+      end
 
-          self
-        end
+      def reload!
+        @translations = nil
 
-        def initialized?
-          !@translations.nil?
-        end
+        self
+      end
 
-        def init_translations
-          @translations = Translation.to_hash
-        end
+      def initialized?
+        !@translations.nil?
+      end
 
-        def translations(do_init: false)
-          init_translations if do_init || !initialized?
-          @translations ||= {}
-        end
+      def init_translations
+        @translations = Translation.to_hash
+      end
 
-      protected
+      def translations(do_init: false)
+        init_translations if do_init || !initialized?
+        @translations ||= {}
+      end
 
-        def lookup(locale, key, scope = [], options = {})
-          key = normalize_flat_keys(locale, key, scope, options[:separator])
-          if key.first == '.'
-            key = key[1..-1]
-          end
-          if key.last == '.'
-            key = key[0..-2]
-          end
+      protected
 
-          if ActiveRecord.config.cache_translations
-            init_translations if @translations.nil? || @translations.empty?
+      def lookup(locale, key, scope = [], options = {})
+        key = normalize_flat_keys(locale, key, scope, options[:separator])
+        key = key[1..-1] if key.first == '.'
+        key = key[0..-2] if key.last == '.'
 
-            keys = ([locale] + key.split(I18n::Backend::Flatten::FLATTEN_SEPARATOR)).map(&:to_sym)
+        if ActiveRecord.config.cache_translations
+          init_translations if @translations.nil? || @translations.empty?
 
-            return translations.dig(*keys)
-          end
+          keys = ([locale] + key.split(I18n::Backend::Flatten::FLATTEN_SEPARATOR)).map(&:to_sym)
 
-          result = if key == ''
-            Translation.locale(locale).all
-          else
-            Translation.locale(locale).lookup(key)
-          end
+          return translations.dig(*keys)
+        end
 
-          if result.empty?
-            nil
-          elsif result.first.key == key
-            result.first.value
-          else
-            result = result.inject({}) do |hash, translation|
-              hash.deep_merge build_translation_hash_by_key(key, translation)
-            end
-            result.deep_symbolize_keys
-          end
+        result = if key == ''
+          Translation.locale(locale).all
+        else
+          Translation.locale(locale).lookup(key)
         end
 
-        def build_translation_hash_by_key(lookup_key, translation)
-          hash = {}
-          if lookup_key == ''
-            chop_range = 0..-1
-          else
-            chop_range = (lookup_key.size + FLATTEN_SEPARATOR.size)..-1
+        if result.empty?
+          nil
+        elsif result.first.key == key
+          result.first.value
+        else
+          result = result.inject({}) do |hash, translation|
+            hash.deep_merge build_translation_hash_by_key(key, translation)
           end
-          translation_nested_keys = translation.key.slice(chop_range).split(FLATTEN_SEPARATOR)
-          translation_nested_keys.each.with_index.inject(hash) do |iterator, (key, index)|
-            iterator[key] = translation_nested_keys[index + 1] ?  {} : translation.value
-            iterator[key]
-          end
-          hash
+          result.deep_symbolize_keys
         end
+      end
 
-        # For a key :'foo.bar.baz' return ['foo', 'foo.bar', 'foo.bar.baz']
-        def expand_keys(key)
-          key.to_s.split(FLATTEN_SEPARATOR).inject([]) do |keys, key|
-            keys << [keys.last, key].compact.join(FLATTEN_SEPARATOR)
-          end
+      def build_translation_hash_by_key(lookup_key, translation)
+        hash = {}
+
+        chop_range = if lookup_key == ''
+          0..-1
+        else
+          (lookup_key.size + FLATTEN_SEPARATOR.size)..-1
         end
+        translation_nested_keys = translation.key.slice(chop_range).split(FLATTEN_SEPARATOR)
+        translation_nested_keys.each.with_index.inject(hash) do |iterator, (key, index)|
+          iterator[key] = translation_nested_keys[index + 1] ?  {} : translation.value
+          iterator[key]
+        end
+
+        hash
       end
 
-      include Implementation
+      # For a key :'foo.bar.baz' return ['foo', 'foo.bar', 'foo.bar.baz']
+      def expand_keys(key)
+        key.to_s.split(FLATTEN_SEPARATOR).inject([]) do |keys, k|
+          keys << [keys.last, k].compact.join(FLATTEN_SEPARATOR)
+        end
+      end
     end
   end
 end
diff --git a/lib/i18n/backend/active_record/configuration.rb b/lib/i18n/backend/active_record/configuration.rb
index 4d4176c9..f3f72fb1 100644
--- a/lib/i18n/backend/active_record/configuration.rb
+++ b/lib/i18n/backend/active_record/configuration.rb
@@ -2,8 +2,7 @@ module I18n
   module Backend
     class ActiveRecord
       class Configuration
-        attr_accessor :cleanup_with_destroy
-        attr_accessor :cache_translations
+        attr_accessor :cleanup_with_destroy, :cache_translations
 
         def initialize
           @cleanup_with_destroy = false
diff --git a/lib/i18n/backend/active_record/missing.rb b/lib/i18n/backend/active_record/missing.rb
index b04e92f7..7f3db4e0 100644
--- a/lib/i18n/backend/active_record/missing.rb
+++ b/lib/i18n/backend/active_record/missing.rb
@@ -36,27 +36,28 @@ module Missing
         include Flatten
 
         def store_default_translations(locale, key, options = {})
-          count, scope, default, separator = options.values_at(:count, :scope, :default, :separator)
+          count, scope, _, separator = options.values_at(:count, :scope, :default, :separator)
           separator ||= I18n.default_separator
           key = normalize_flat_keys(locale, key, scope, separator)
 
-          unless ActiveRecord::Translation.locale(locale).lookup(key).exists?
-            interpolations = options.keys - I18n::RESERVED_KEYS
-            keys = count ? I18n.t('i18n.plural.keys', :locale => locale).map { |k| [key, k].join(FLATTEN_SEPARATOR) } : [key]
-            keys.each { |key| store_default_translation(locale, key, interpolations) }
-          end
+          return if ActiveRecord::Translation.locale(locale).lookup(key).exists?
+
+          interpolations = options.keys - I18n::RESERVED_KEYS
+          keys = count ? I18n.t('i18n.plural.keys', locale: locale).map { |k| [key, k].join(FLATTEN_SEPARATOR) } : [key]
+          keys.each { |k| store_default_translation(locale, k, interpolations) }
         end
 
         def store_default_translation(locale, key, interpolations)
-          translation = ActiveRecord::Translation.new :locale => locale.to_s, :key => key
+          translation = ActiveRecord::Translation.new locale: locale.to_s, key: key
           translation.interpolations = interpolations
           translation.save
         end
 
         def translate(locale, key, options = {})
           result = catch(:exception) { super }
+
           if result.is_a?(I18n::MissingTranslation)
-            self.store_default_translations(locale, key, options)
+            store_default_translations(locale, key, options)
             throw(:exception, result)
           else
             result
diff --git a/lib/i18n/backend/active_record/translation.rb b/lib/i18n/backend/active_record/translation.rb
index c3b7e616..7d990240 100644
--- a/lib/i18n/backend/active_record/translation.rb
+++ b/lib/i18n/backend/active_record/translation.rb
@@ -57,12 +57,12 @@ class Translation < ::ActiveRecord::Base
 
         class << self
           def locale(locale)
-            where(:locale => locale.to_s)
+            where(locale: locale.to_s)
           end
 
           def lookup(keys, *separator)
             column_name = connection.quote_column_name('key')
-            keys = Array(keys).map! { |key| key.to_s }
+            keys = Array(keys).map!(&:to_s)
 
             unless separator.empty?
               warn "[DEPRECATION] Giving a separator to Translation.lookup is deprecated. " <<
@@ -91,7 +91,7 @@ def to_hash
         end
 
         def interpolates?(key)
-          self.interpolations.include?(key) if self.interpolations
+          interpolations&.include?(key)
         end
 
         def value
diff --git a/test/active_record_test.rb b/test/active_record_test.rb
index 8b3dc9cc..9b449e0d 100644
--- a/test/active_record_test.rb
+++ b/test/active_record_test.rb
@@ -4,13 +4,15 @@ class I18nBackendActiveRecordTest < I18n::TestCase
   def setup
     super
 
+    I18n::Backend::ActiveRecord::Translation.destroy_all
     I18n.backend = I18n::Backend::ActiveRecord.new
-    store_translations(:en, :foo => { :bar => 'bar', :baz => 'baz' })
+
+    store_translations(:en, foo: { bar: 'bar', baz: 'baz' })
   end
 
   def teardown
-    I18n::Backend::ActiveRecord::Translation.destroy_all
     I18n::Backend::ActiveRecord.instance_variable_set :@config, I18n::Backend::ActiveRecord::Configuration.new
+
     super
   end
 
@@ -22,22 +24,20 @@ def setup
     end
 
     test "store_translations does not allow ambiguous keys (1)" do
-      I18n::Backend::ActiveRecord::Translation.delete_all
-      I18n.backend.store_translations(:en, :foo => 'foo')
-      I18n.backend.store_translations(:en, :foo => { :bar => 'bar' })
-      I18n.backend.store_translations(:en, :foo => { :baz => 'baz' })
+      store_translations(:en, foo: 'foo')
+      store_translations(:en, foo: { bar: 'bar' })
+      store_translations(:en, foo: { baz: 'baz' })
 
       translations = I18n::Backend::ActiveRecord::Translation.locale(:en).lookup('foo').all
       assert_equal %w(bar baz), translations.map(&:value)
 
-      assert_equal({ :bar => 'bar', :baz => 'baz' }, I18n.t(:foo))
+      assert_equal({ bar: 'bar', baz: 'baz' }, I18n.t(:foo))
     end
 
     test "store_translations does not allow ambiguous keys (2)" do
-      I18n::Backend::ActiveRecord::Translation.delete_all
-      I18n.backend.store_translations(:en, :foo => { :bar => 'bar' })
-      I18n.backend.store_translations(:en, :foo => { :baz => 'baz' })
-      I18n.backend.store_translations(:en, :foo => 'foo')
+      store_translations(:en, foo: { bar: 'bar' })
+      store_translations(:en, foo: { baz: 'baz' })
+      store_translations(:en, foo: 'foo')
 
       translations = I18n::Backend::ActiveRecord::Translation.locale(:en).lookup('foo').all
       assert_equal %w(foo), translations.map(&:value)
@@ -46,8 +46,9 @@ def setup
     end
 
     test "can store translations with keys that are translations containing special chars" do
-      I18n.backend.store_translations(:es, :"Pagina's" => "Pagina's" )
-      assert_equal "Pagina's", I18n.t(:"Pagina's", :locale => :es)
+      store_translations(:es, "Pagina's": "Pagina's")
+
+      assert_equal "Pagina's", I18n.t(:"Pagina's", locale: :es)
     end
 
     test "missing translations table does not cause an error in #available_locales" do
@@ -60,12 +61,11 @@ def setup
     end
 
     test "available_locales returns uniq locales" do
-      I18n::Backend::ActiveRecord::Translation.delete_all
-      I18n.backend.store_translations(:en, :foo => { :bar => 'bar' })
-      I18n.backend.store_translations(:en, :foo => { :baz => 'baz' })
-      I18n.backend.store_translations(:de, :foo1 => 'foo')
-      I18n.backend.store_translations(:de, :foo2 => 'foo')
-      I18n.backend.store_translations(:uk, :foo3 => 'foo')
+      store_translations(:en, foo: { bar: 'bar' })
+      store_translations(:en, foo: { baz: 'baz' })
+      store_translations(:de, foo1: 'foo')
+      store_translations(:de, foo2: 'foo')
+      store_translations(:uk, foo3: 'foo')
 
       available_locales = I18n::Backend::ActiveRecord::Translation.available_locales
       assert_equal 3, available_locales.size
@@ -87,24 +87,27 @@ def setup
     end
 
     test "fetching subtree of translations" do
-      I18n::Backend::ActiveRecord::Translation.delete_all
-      I18n.backend.store_translations(:en, foo: { bar: { fizz: 'buzz', spuz: 'zazz' }, baz: { fizz: 'buzz' } })
+      store_translations(:en, foo: { bar: { fizz: 'buzz', spuz: 'zazz' }, baz: { fizz: 'buzz' } })
+
       assert_equal I18n.t(:foo), { bar: { fizz: 'buzz', spuz: 'zazz' }, baz: { fizz: 'buzz' } }
     end
 
     test "build_translation_hash_by_key" do
       translation = I18n::Backend::ActiveRecord::Translation.new(value: 'translation', key: 'foo.bar.fizz.buzz')
       expected_hash = { 'bar' => { 'fizz' => { 'buzz' => 'translation' } } }
+
       assert_equal I18n.backend.send(:build_translation_hash_by_key, 'foo', translation), expected_hash
     end
 
     test "returning all keys via ." do
-      expected_hash = {:foo => { :bar => 'bar', :baz => 'baz' }}
+      expected_hash = { foo: { bar: 'bar', baz: 'baz' }}
+
       assert_equal expected_hash, I18n.t('.')
     end
 
     test "accessing keys with a trailing/leading period" do
-      expected_hash = { :bar => 'bar', :baz => 'baz' }
+      expected_hash = { bar: 'bar', baz: 'baz' }
+
       assert_equal expected_hash, I18n.t('foo')
       assert_equal expected_hash, I18n.t('.foo')
       assert_equal expected_hash, I18n.t('foo.')
@@ -121,23 +124,28 @@ def setup
 
     test "intially unitinitialized" do
       refute I18n.backend.initialized?
+
       I18n.backend.init_translations
       assert I18n.backend.initialized?
+
       I18n.backend.reload!
       refute I18n.backend.initialized?
+
       I18n.backend.init_translations
       assert I18n.backend.initialized?
     end
 
     test "translations returns all translations" do
-      expected_hash = { :en => { :foo => { :bar => 'bar', :baz => 'baz' } } }
+      expected_hash = { en: { foo: { bar: 'bar', baz: 'baz' } } }
       I18n.backend.init_translations
+
       assert_equal expected_hash, I18n.backend.send(:translations)
       assert I18n.backend.initialized?
     end
 
     test "translations initialized with do_init argument" do
-      expected_hash = { :en => { :foo => { :bar => 'bar', :baz => 'baz' } } }
+      expected_hash = { en: { foo: { bar: 'bar', baz: 'baz' } } }
+
       refute I18n.backend.initialized?
       assert_equal expected_hash, I18n.backend.send(:translations, do_init: true)
       assert I18n.backend.initialized?
diff --git a/test/api_test.rb b/test/api_test.rb
index 26164463..8c072716 100644
--- a/test/api_test.rb
+++ b/test/api_test.rb
@@ -3,6 +3,7 @@
 class I18nActiveRecordApiTest < I18n::TestCase
   def setup
     I18n.backend = I18n::Backend::ActiveRecord.new
+
     super
   end
 
diff --git a/test/missing_test.rb b/test/missing_test.rb
index 3b68e88e..bd4a8f46 100644
--- a/test/missing_test.rb
+++ b/test/missing_test.rb
@@ -8,13 +8,15 @@ class BackendWithMissing < I18n::Backend::ActiveRecord
   def setup
     super
 
+    I18n::Backend::ActiveRecord::Translation.destroy_all
     I18n.backend = BackendWithMissing.new
-    store_translations(:en, :bar => 'Bar', :i18n => { :plural => { :keys => [:zero, :one, :other] } })
+
+    store_translations(:en, bar: 'Bar', i18n: { plural: { keys: [:zero, :one, :other] } })
   end
 
   def teardown
-    I18n::Backend::ActiveRecord::Translation.destroy_all
     I18n::Backend::ActiveRecord.instance_variable_set :@config, I18n::Backend::ActiveRecord::Configuration.new
+
     super
   end
 
@@ -26,9 +28,10 @@ def setup
     end
 
     test "can persist interpolations" do
-      translation = I18n::Backend::ActiveRecord::Translation.new(:key => 'foo', :value => 'bar', :locale => :en)
+      translation = I18n::Backend::ActiveRecord::Translation.new(key: 'foo', value: 'bar', locale: :en)
       translation.interpolations = %w(count name)
       translation.save
+
       assert translation.valid?
     end
 
@@ -41,45 +44,52 @@ def setup
 
     test "lookup does not persist the key twice" do
       2.times { I18n.t('foo.bar.baz') }
+
       assert_equal 3, I18n::Backend::ActiveRecord::Translation.count
       assert I18n::Backend::ActiveRecord::Translation.locale(:en).find_by_key('foo.bar.baz')
     end
 
     test "lookup persists interpolation keys when looked up directly" do
-      I18n.t('foo.bar.baz', :cow => "lucy" )  # creates stub translation.
+      I18n.t('foo.bar.baz', cow: "lucy" )  # creates stub translation.
       translation_stub = I18n::Backend::ActiveRecord::Translation.locale(:en).lookup('foo.bar.baz').first
+
       assert translation_stub.interpolates?(:cow)
     end
 
     test "creates one stub per pluralization" do
-      I18n.t('foo', :count => 999)
+      I18n.t('foo', count: 999)
       translations = I18n::Backend::ActiveRecord::Translation.locale(:en).where key: %w{ foo.zero foo.one foo.other }
+
       assert_equal 3, translations.length
     end
 
     test "creates no stub for base key in pluralization" do
-      I18n.t('foo', :count => 999)
+      I18n.t('foo', count: 999)
+
       assert_equal 3, I18n::Backend::ActiveRecord::Translation.locale(:en).lookup("foo").count
       assert !I18n::Backend::ActiveRecord::Translation.locale(:en).find_by_key("foo")
     end
 
     test "creates a stub when a custom separator is used" do
-      I18n.t('foo|baz', :separator => '|')
-      I18n::Backend::ActiveRecord::Translation.locale(:en).lookup("foo.baz").first.update(:value => 'baz!')
-      assert_equal 'baz!', I18n.t('foo|baz', :separator => '|')
+      I18n.t('foo|baz', separator: '|')
+      I18n::Backend::ActiveRecord::Translation.locale(:en).lookup("foo.baz").first.update(value: 'baz!')
+
+      assert_equal 'baz!', I18n.t('foo|baz', separator: '|')
     end
 
     test "creates a stub per pluralization when a custom separator is used" do
-      I18n.t('foo|bar', :count => 999, :separator => '|')
+      I18n.t('foo|bar', count: 999, separator: '|')
       translations = I18n::Backend::ActiveRecord::Translation.locale(:en).where key: %w{ foo.bar.zero foo.bar.one foo.bar.other }
+
       assert_equal 3, translations.length
     end
 
     test "creates a stub when a custom separator is used and the key contains the flatten separator (a dot character)" do
       key = 'foo|baz.zab'
-      I18n.t(key, :separator => '|')
-      I18n::Backend::ActiveRecord::Translation.locale(:en).lookup("foo.baz\001zab").first.update(:value => 'baz!')
-      assert_equal 'baz!', I18n.t(key, :separator => '|')
+      I18n.t(key, separator: '|')
+      I18n::Backend::ActiveRecord::Translation.locale(:en).lookup("foo.baz\001zab").first.update(value: 'baz!')
+
+      assert_equal 'baz!', I18n.t(key, separator: '|')
     end
   end
 
diff --git a/test/test_helper.rb b/test/test_helper.rb
index f3197f2e..8039c70f 100644
--- a/test/test_helper.rb
+++ b/test/test_helper.rb
@@ -15,34 +15,48 @@
   puts "can't use ActiveRecord backend because: #{e.message}"
 rescue ::ActiveRecord::ConnectionNotEstablished
   require 'i18n/backend/active_record'
+
   case ENV['DB']
   when 'postgres'
-    ::ActiveRecord::Base.establish_connection adapter: 'postgresql', database: 'i18n_unittest', username: ENV['PG_USER'] || 'i18n', password: '', host: 'localhost'
+    ::ActiveRecord::Base.establish_connection(
+      adapter: 'postgresql',
+      database: 'i18n_unittest',
+      username: ENV['PG_USER'] || 'postgres',
+      password: ENV['PG_PASSWORD'] || 'postgres',
+      host: 'localhost'
+    )
   when 'mysql'
-    ::ActiveRecord::Base.establish_connection adapter: 'mysql2', database: 'i18n_unittest', username: 'root', password: '', host: 'localhost'
+    ::ActiveRecord::Base.establish_connection(
+      adapter: 'mysql2',
+      database: 'i18n_unittest',
+      username: ENV['MYSQL_USER'] || 'root',
+      password: ENV['MYSQL_PASSWORD'] || '',
+      host: '127.0.0.1'
+    )
   else
     ::ActiveRecord::Base.establish_connection adapter: 'sqlite3', database: ':memory:'
   end
+
   ::ActiveRecord::Migration.verbose = false
-  ::ActiveRecord::Schema.define(:version => 1) do
-    create_table :translations, :force => true do |t|
+  ::ActiveRecord::Schema.define(version: 1) do
+    create_table :translations, force: true do |t|
       t.string :locale
       t.string :key
       t.text :value
       t.text :interpolations
-      t.boolean :is_proc, :default => false
+      t.boolean :is_proc, default: false
     end
-    add_index :translations, [:locale, :key], :unique => true
+    add_index :translations, [:locale, :key], unique: true
   end
 end
 
 TEST_CASE = defined?(Minitest::Test) ? Minitest::Test : MiniTest::Unit::TestCase
 
 class TEST_CASE
-  alias :assert_raise :assert_raises
-  alias :assert_not_equal :refute_equal
+  alias assert_raise assert_raises
+  alias assert_not_equal refute_equal
 
-  def assert_nothing_raised(*args)
+  def assert_nothing_raised(*_args)
     yield
   end
 end