diff --git a/Gemfile b/Gemfile
index 2535d020..98363e07 100644
--- a/Gemfile
+++ b/Gemfile
@@ -11,10 +11,10 @@ version = ENV['RAILS_VERSION'] || 'default'
 platforms :ruby do
   gem 'pg'
 
-  if version.start_with?('4.2', '5.0')
-    gem 'sqlite3', '~> 1.3.13'
+  if version.start_with?('8.1')
+    gem 'sqlite3', '>= 2.1'
   else
-    gem 'sqlite3', '~> 1.4'
+    gem 'sqlite3', '~> 1.3.13'
   end
 end
 
@@ -24,6 +24,7 @@ when 'master'
   gem 'arel', { git: 'https://github.com/rails/arel.git' }
 when 'default'
   gem 'railties', '>= 6.0'
+  gem 'csv'
 else
   gem 'railties', "~> #{version}"
-end
\ No newline at end of file
+end
diff --git a/lib/jsonapi-resources.rb b/lib/jsonapi-resources.rb
index 401d9bbc..35818bf2 100644
--- a/lib/jsonapi-resources.rb
+++ b/lib/jsonapi-resources.rb
@@ -43,3 +43,4 @@
 require 'jsonapi/resource_set'
 require 'jsonapi/path'
 require 'jsonapi/path_segment'
+require 'jsonapi/deprecator'
diff --git a/lib/jsonapi/active_relation_resource.rb b/lib/jsonapi/active_relation_resource.rb
index 581ed1e0..4a2aeb09 100644
--- a/lib/jsonapi/active_relation_resource.rb
+++ b/lib/jsonapi/active_relation_resource.rb
@@ -847,7 +847,16 @@ def alias_table_field(table, field, quoted = false)
       end
 
       def quote(field)
-        "\"#{field.to_s}\""
+        if oracle?
+          "\"#{field.to_s.upcase}\""
+        else
+          "\"#{field.to_s}\""
+        end
+      end
+
+      def oracle?
+        defined?(ActiveRecord::Base.connection) &&
+          ActiveRecord::Base.connection.adapter_name =~ /oracle/i
       end
 
       def apply_filters(records, filters, options = {})
diff --git a/lib/jsonapi/basic_resource.rb b/lib/jsonapi/basic_resource.rb
index 2eeba5c5..0d55879d 100644
--- a/lib/jsonapi/basic_resource.rb
+++ b/lib/jsonapi/basic_resource.rb
@@ -547,7 +547,7 @@ def attribute(attribute_name, options = {})
         check_reserved_attribute_name(attr)
 
         if (attr == :id) && (options[:format].nil?)
-          ActiveSupport::Deprecation.warn('Id without format is no longer supported. Please remove ids from attributes, or specify a format.')
+          JSONAPI.deprecator.warn('Id without format is no longer supported. Please remove ids from attributes, or specify a format.')
         end
 
         check_duplicate_attribute_name(attr) if options[:format].nil?
@@ -609,7 +609,7 @@ def has_one(*attrs)
       end
 
       def belongs_to(*attrs)
-        ActiveSupport::Deprecation.warn "In #{name} you exposed a `has_one` relationship "\
+        JSONAPI.deprecator.warn"In #{name} you exposed a `has_one` relationship "\
                                         " using the `belongs_to` class method. We think `has_one`" \
                                         " is more appropriate. If you know what you're doing," \
                                         " and don't want to see this warning again, override the" \
diff --git a/lib/jsonapi/configuration.rb b/lib/jsonapi/configuration.rb
index 6cd5d8e1..675d4331 100644
--- a/lib/jsonapi/configuration.rb
+++ b/lib/jsonapi/configuration.rb
@@ -241,18 +241,18 @@ def default_processor_klass_name=(default_processor_klass_name)
     end
 
     def allow_include=(allow_include)
-      ActiveSupport::Deprecation.warn('`allow_include` has been replaced by `default_allow_include_to_one` and `default_allow_include_to_many` options.')
+      JSONAPI.deprecator.warn('`allow_include` has been replaced by `default_allow_include_to_one` and `default_allow_include_to_many` options.')
       @default_allow_include_to_one = allow_include
       @default_allow_include_to_many = allow_include
     end
 
     def whitelist_all_exceptions=(allow_all_exceptions)
-      ActiveSupport::Deprecation.warn('`whitelist_all_exceptions` has been replaced by `allow_all_exceptions`')
+      JSONAPI.deprecator.warn('`whitelist_all_exceptions` has been replaced by `allow_all_exceptions`')
       @allow_all_exceptions = allow_all_exceptions
     end
 
     def exception_class_whitelist=(exception_class_allowlist)
-      ActiveSupport::Deprecation.warn('`exception_class_whitelist` has been replaced by `exception_class_allowlist`')
+      JSONAPI.deprecator.warn('`exception_class_whitelist` has been replaced by `exception_class_allowlist`')
       @exception_class_allowlist = exception_class_allowlist
     end
 
@@ -315,11 +315,13 @@ def exception_class_whitelist=(exception_class_allowlist)
 
   class << self
     attr_accessor :configuration
-  end
 
-  @configuration ||= Configuration.new
+    def configuration
+      @configuration ||= Configuration.new
+    end
+  end
 
   def self.configure
-    yield(@configuration)
+    yield(configuration)
   end
 end
diff --git a/lib/jsonapi/deprecator.rb b/lib/jsonapi/deprecator.rb
new file mode 100644
index 00000000..856761d6
--- /dev/null
+++ b/lib/jsonapi/deprecator.rb
@@ -0,0 +1,5 @@
+module JSONAPI
+  def self.deprecator
+    @deprecator ||= ActiveSupport::Deprecation.new('1.0', 'jsonapi-resources')
+  end
+end
diff --git a/lib/jsonapi/exceptions.rb b/lib/jsonapi/exceptions.rb
index e917118c..a0c437ee 100644
--- a/lib/jsonapi/exceptions.rb
+++ b/lib/jsonapi/exceptions.rb
@@ -498,7 +498,7 @@ def errors
 
       def json_api_error(attr_key, message)
         create_error_object(code: JSONAPI::VALIDATION_ERROR,
-                            status: :unprocessable_entity,
+                            status: :unprocessable_content,
                             title: message,
                             detail: detail(attr_key, message),
                             source: { pointer: pointer(attr_key) },
@@ -532,7 +532,7 @@ def general_error?(attr_key)
     class SaveFailed < Error
       def errors
         [create_error_object(code: JSONAPI::SAVE_FAILED,
-                             status: :unprocessable_entity,
+                             status: :unprocessable_content,
                              title: I18n.translate('jsonapi-resources.exceptions.save_failed.title',
                                                    default: 'Save failed or was cancelled'),
                              detail: I18n.translate('jsonapi-resources.exceptions.save_failed.detail',
diff --git a/lib/jsonapi/routing_ext.rb b/lib/jsonapi/routing_ext.rb
index b0b94013..221f3bde 100644
--- a/lib/jsonapi/routing_ext.rb
+++ b/lib/jsonapi/routing_ext.rb
@@ -46,7 +46,7 @@ def jsonapi_resource(*resources, &_block)
             options[:except] << :destroy unless options[:except].include?(:destroy) || options[:except].include?('destroy')
           end
 
-          resource @resource_type, options do
+          resource @resource_type, **options do
             # :nocov:
             if @scope.respond_to? :[]=
               # Rails 4
@@ -59,7 +59,7 @@ def jsonapi_resource(*resources, &_block)
               end
             else
               # Rails 5
-              jsonapi_resource_scope(SingletonResource.new(@resource_type, api_only?, @scope[:shallow], options), @resource_type) do
+              jsonapi_resource_scope(SingletonResource.new(@resource_type, api_only?, @scope[:shallow], **options), @resource_type) do
                 if block_given?
                   yield
                 else
@@ -121,7 +121,7 @@ def jsonapi_resources(*resources, &_block)
             options[:except] << :destroy unless options[:except].include?(:destroy) || options[:except].include?('destroy')
           end
 
-          resources @resource_type, options do
+          resources @resource_type, **options do
             # :nocov:
             if @scope.respond_to? :[]=
               # Rails 4
@@ -133,7 +133,7 @@ def jsonapi_resources(*resources, &_block)
               end
             else
               # Rails 5
-              jsonapi_resource_scope(Resource.new(@resource_type, api_only?, @scope[:shallow], options), @resource_type) do
+              jsonapi_resource_scope(Resource.new(@resource_type, api_only?, @scope[:shallow], **options), @resource_type) do
                 if block_given?
                   yield
                 else
diff --git a/test/controllers/controller_test.rb b/test/controllers/controller_test.rb
index e2568f97..a2f22066 100644
--- a/test/controllers/controller_test.rb
+++ b/test/controllers/controller_test.rb
@@ -761,7 +761,7 @@ def test_create_link_to_missing_object
         }
       }
 
-    assert_response :unprocessable_entity
+    assert_response :unprocessable_content
     # TODO: check if this validation is working
     assert_match /author - can't be blank/, response.body
     assert_nil response.location
@@ -864,7 +864,7 @@ def test_create_with_invalid_data
         }
       }
 
-    assert_response :unprocessable_entity
+    assert_response :unprocessable_content
 
     assert_equal "/data/relationships/author", json_response['errors'][0]['source']['pointer']
     assert_equal "can't be blank", json_response['errors'][0]['title']
@@ -2019,7 +2019,7 @@ def test_delete_with_validation_error_base
 
     assert_equal "can't destroy me", json_response['errors'][0]['title']
     assert_equal "/data", json_response['errors'][0]['source']['pointer']
-    assert_response :unprocessable_entity
+    assert_response :unprocessable_content
   end
 
   def test_delete_with_validation_error_attr
@@ -2028,7 +2028,7 @@ def test_delete_with_validation_error_attr
 
     assert_equal "is locked", json_response['errors'][0]['title']
     assert_equal "/data/attributes/title", json_response['errors'][0]['source']['pointer']
-    assert_response :unprocessable_entity
+    assert_response :unprocessable_content
   end
 
   def test_delete_single
@@ -2631,7 +2631,7 @@ def test_create_validations_missing_attribute
         }
       }
 
-    assert_response :unprocessable_entity
+    assert_response :unprocessable_content
     assert_equal 2, json_response['errors'].size
     assert_equal JSONAPI::VALIDATION_ERROR, json_response['errors'][0]['code']
     assert_equal JSONAPI::VALIDATION_ERROR, json_response['errors'][1]['code']
@@ -2653,7 +2653,7 @@ def test_update_validations_missing_attribute
         }
       }
 
-    assert_response :unprocessable_entity
+    assert_response :unprocessable_content
     assert_equal 1, json_response['errors'].size
     assert_equal JSONAPI::VALIDATION_ERROR, json_response['errors'][0]['code']
     assert_match /name - can't be blank/, response.body
@@ -3183,7 +3183,7 @@ def test_create_with_invalid_data
         }
       }
 
-    assert_response :unprocessable_entity
+    assert_response :unprocessable_content
 
     assert_equal "/data/attributes/spouse-name", json_response['errors'][0]['source']['pointer']
     assert_equal "can't be blank", json_response['errors'][0]['title']
@@ -3779,7 +3779,7 @@ def test_save_model_callbacks_fail
         }
       }
 
-    assert_response :unprocessable_entity
+    assert_response :unprocessable_content
     assert_match /Save failed or was cancelled/, json_response['errors'][0]['detail']
   end
 end
@@ -4077,7 +4077,7 @@ def test_delete_with_validation_error_base_on_resource
 
     assert_equal "can't destroy me", json_response['errors'][0]['title']
     assert_equal "/data/attributes/base", json_response['errors'][0]['source']['pointer']
-    assert_response :unprocessable_entity
+    assert_response :unprocessable_content
   end
 end
 
diff --git a/test/fixtures/active_record.rb b/test/fixtures/active_record.rb
index f8959317..3f81501c 100644
--- a/test/fixtures/active_record.rb
+++ b/test/fixtures/active_record.rb
@@ -52,7 +52,7 @@
   end
 
   create_table :posts, force: true do |t|
-    t.string     :title, length: 255
+    t.string     :title, limit: 255
     t.text       :body
     t.integer    :author_id
     t.integer    :parent_post_id
@@ -324,8 +324,8 @@
 
   create_table :related_things, force: true  do |t|
     t.string :name
-    t.references :from, references: :thing
-    t.references :to, references: :thing
+    t.references :from, foreign_key: { to_table: :things }
+    t.references :to, foreign_key: { to_table: :things }
 
     t.timestamps null: false
   end
diff --git a/test/integration/requests/request_test.rb b/test/integration/requests/request_test.rb
index b7895608..4cdbe331 100644
--- a/test/integration/requests/request_test.rb
+++ b/test/integration/requests/request_test.rb
@@ -578,7 +578,7 @@ def test_put_invalid_json
 
     assert_equal 400, status
     assert_equal 'Bad Request', json_response['errors'][0]['title']
-    assert_match 'unexpected token at', json_response['errors'][0]['detail']
+    assert_match "expected ',' or '}' after object value", json_response['errors'][0]['detail']
   end
 
   def test_put_valid_json_but_array
@@ -1367,7 +1367,11 @@ def test_deprecated_include_parameter_not_allowed
   end
 
   def test_deprecated_include_message
-    ActiveSupport::Deprecation.silenced = false
+    if ActiveSupport::Deprecation.respond_to?(:silenced=)
+      ActiveSupport::Deprecation.silenced = false
+    else
+      JSONAPI.deprecator.silenced = false
+    end
     original_config = JSONAPI.configuration.dup
     _out, err = capture_io do
       eval <<-CODE
@@ -1377,7 +1381,11 @@ def test_deprecated_include_message
     assert_match /DEPRECATION WARNING: `allow_include` has been replaced by `default_allow_include_to_one` and `default_allow_include_to_many` options./, err
   ensure
     JSONAPI.configuration = original_config
-    ActiveSupport::Deprecation.silenced = true
+    if ActiveSupport::Deprecation.respond_to?(:silenced=)
+      ActiveSupport::Deprecation.silenced = true
+    else
+      JSONAPI.deprecator.silenced = true
+    end
   end
 
 
diff --git a/test/test_helper.rb b/test/test_helper.rb
index c1faea37..c82caeb0 100644
--- a/test/test_helper.rb
+++ b/test/test_helper.rb
@@ -23,7 +23,6 @@
 ENV['DATABASE_URL'] ||= "sqlite3:test_db"
 
 require 'active_record/railtie'
-require 'rails/test_help'
 require 'minitest/mock'
 require 'jsonapi-resources'
 require 'pry'
@@ -42,7 +41,11 @@
   config.json_key_format = :camelized_key
 end
 
-ActiveSupport::Deprecation.silenced = true
+if ActiveSupport::Deprecation.respond_to?(:silenced=)
+  ActiveSupport::Deprecation.silenced = true
+else
+  JSONAPI.deprecator.silenced = true
+end
 
 puts "Testing With RAILS VERSION #{Rails.version}"
 
@@ -56,7 +59,7 @@ class TestApp < Rails::Application
   config.action_controller.action_on_unpermitted_parameters = :raise
 
   ActiveRecord::Schema.verbose = false
-  config.active_record.schema_format = :none
+  config.active_record.schema_format = Rails::VERSION::MAJOR >= 8 ? :ruby : :none
   config.active_support.test_order = :random
 
   config.active_support.halt_callback_chains_on_return_false = false
@@ -67,9 +70,6 @@ class TestApp < Rails::Application
   end
 end
 
-DatabaseCleaner.allow_remote_database_url = true
-DatabaseCleaner.strategy = :transaction
-
 module MyEngine
   class Engine < ::Rails::Engine
     isolate_namespace MyEngine
@@ -191,6 +191,13 @@ def show_queries
 end
 
 TestApp.initialize!
+require 'rails/test_help'
+
+# Disable foreign key constraints for SQLite tests
+ActiveRecord::Base.connection.execute('PRAGMA foreign_keys = OFF') if ActiveRecord::Base.connection.adapter_name == 'SQLite'
+
+DatabaseCleaner.allow_remote_database_url = true
+DatabaseCleaner.strategy = :transaction
 
 require File.expand_path('../fixtures/active_record', __FILE__)
 
@@ -460,12 +467,12 @@ def run_in_transaction?
     true
   end
 
-  self.fixture_path = "#{Rails.root}/fixtures"
+  self.fixture_paths = ["#{Rails.root}/fixtures"]
   fixtures :all
 end
 
 class ActiveSupport::TestCase
-  self.fixture_path = "#{Rails.root}/fixtures"
+  self.fixture_paths = ["#{Rails.root}/fixtures"]
   fixtures :all
   setup do
     @routes = TestApp.routes
@@ -473,7 +480,7 @@ class ActiveSupport::TestCase
 end
 
 class ActionDispatch::IntegrationTest
-  self.fixture_path = "#{Rails.root}/fixtures"
+  self.fixture_paths = ["#{Rails.root}/fixtures"]
   fixtures :all
 
   def assert_jsonapi_response(expected_status, msg = nil)
diff --git a/test/unit/active_relation_resource_finder/join_manager_test.rb b/test/unit/active_relation_resource_finder/join_manager_test.rb
index 840c90ee..5dfc9629 100644
--- a/test/unit/active_relation_resource_finder/join_manager_test.rb
+++ b/test/unit/active_relation_resource_finder/join_manager_test.rb
@@ -4,16 +4,7 @@
 class JoinTreeTest < ActiveSupport::TestCase
 
   def db_true
-    case ActiveRecord::Base.connection.adapter_name
-      when 'SQLite'
-        if Rails::VERSION::MAJOR >= 6 || (Rails::VERSION::MAJOR >= 5 && ActiveRecord::VERSION::MINOR >= 2)
-          "1"
-        else
-          "'t'"
-        end
-      when 'PostgreSQL'
-        'TRUE'
-    end
+    ActiveRecord::Base.connection.quoted_true
   end
 
   def test_no_added_joins
diff --git a/test/unit/resource/resource_test.rb b/test/unit/resource/resource_test.rb
index df2df173..c48ac1c4 100644
--- a/test/unit/resource/resource_test.rb
+++ b/test/unit/resource/resource_test.rb
@@ -433,8 +433,12 @@ def test_key_type_proc
   end
 
   def test_id_attr_deprecation
+    if ActiveSupport::Deprecation.respond_to?(:silenced=)
+      ActiveSupport::Deprecation.silenced = false
+    else
+      JSONAPI.deprecator.silenced = false
+    end
 
-    ActiveSupport::Deprecation.silenced = false
     _out, err = capture_io do
       eval <<-CODE
         class ProblemResource < JSONAPI::Resource
@@ -442,10 +446,14 @@ class ProblemResource < JSONAPI::Resource
         end
       CODE
     end
-    assert_match /DEPRECATION WARNING: Id without format is no longer supported. Please remove ids from attributes, or specify a format./, err
-  ensure
-    ActiveSupport::Deprecation.silenced = true
-  end
+    assert_match /Id without format is no longer supported\. Please remove ids from attributes, or specify a format\./, err
+    ensure
+      if ActiveSupport::Deprecation.respond_to?(:silenced=)
+        ActiveSupport::Deprecation.silenced = true
+      else
+        JSONAPI.deprecator.silenced = true
+      end
+    end
 
   def test_id_attr_with_format
     _out, err = capture_io do