diff --git a/lib/dynamoid/transaction_write.rb b/lib/dynamoid/transaction_write.rb
index ccff937c..4de4a61a 100644
--- a/lib/dynamoid/transaction_write.rb
+++ b/lib/dynamoid/transaction_write.rb
@@ -14,7 +14,7 @@ class TransactionWrite
     attr_reader :actions
 
     def self.execute
-      transaction = self.new
+      transaction = new
       yield transaction
       transaction.commit
     end
@@ -68,12 +68,12 @@ def create(model_class, attributes = {}, &block)
       end
     end
 
-    def upsert(model_class, hash_key, range_key = nil, attributes)
+    def upsert(model_class, hash_key, range_key = nil, attributes) # rubocop:disable Style/OptionalArguments
       action = Dynamoid::TransactionWrite::Upsert.new(model_class, hash_key, range_key, attributes)
       register_action action
     end
 
-    def update_fields(model_class, hash_key, range_key = nil, attributes)
+    def update_fields(model_class, hash_key, range_key = nil, attributes) # rubocop:disable Style/OptionalArguments
       action = Dynamoid::TransactionWrite::UpdateFields.new(model_class, hash_key, range_key, attributes)
       register_action action
     end
@@ -89,13 +89,12 @@ def update_attributes!(model, attributes)
     end
 
     def delete(model_or_model_class, hash_key = nil, range_key = nil)
-      if model_or_model_class.is_a? Class
-        action = Dynamoid::TransactionWrite::DeleteWithPrimaryKey.new(model_or_model_class, hash_key, range_key)
-        register_action action
-      else
-        action = Dynamoid::TransactionWrite::DeleteWithInstance.new(model_or_model_class)
-        register_action action
-      end
+      action = if model_or_model_class.is_a? Class
+                 Dynamoid::TransactionWrite::DeleteWithPrimaryKey.new(model_or_model_class, hash_key, range_key)
+               else
+                 Dynamoid::TransactionWrite::DeleteWithInstance.new(model_or_model_class)
+               end
+      register_action action
     end
 
     def destroy!(model)
diff --git a/lib/dynamoid/transaction_write/create.rb b/lib/dynamoid/transaction_write/create.rb
index f05e4a01..d4838a2f 100644
--- a/lib/dynamoid/transaction_write/create.rb
+++ b/lib/dynamoid/transaction_write/create.rb
@@ -7,7 +7,7 @@ def initialize(model_class, attributes = {}, **options, &block)
         @model = model_class.new(attributes)
 
         if block
-          block.call(@model)
+          yield(@model)
         end
 
         @save_action = Save.new(@model, **options)
diff --git a/lib/dynamoid/transaction_write/delete_with_primary_key.rb b/lib/dynamoid/transaction_write/delete_with_primary_key.rb
index 56d83d51..a7e72e99 100644
--- a/lib/dynamoid/transaction_write/delete_with_primary_key.rb
+++ b/lib/dynamoid/transaction_write/delete_with_primary_key.rb
@@ -13,8 +13,7 @@ def on_registration
         validate_primary_key!
       end
 
-      def on_completing
-      end
+      def on_completing; end
 
       def aborted?
         false
diff --git a/lib/dynamoid/transaction_write/destroy.rb b/lib/dynamoid/transaction_write/destroy.rb
index e3bc4edf..69e26989 100644
--- a/lib/dynamoid/transaction_write/destroy.rb
+++ b/lib/dynamoid/transaction_write/destroy.rb
@@ -26,6 +26,7 @@ def on_registration
 
       def on_completing
         return if @aborted
+
         @model.destroyed = true
       end
 
@@ -39,19 +40,19 @@ def skip?
 
       def observable_by_user_result
         return false if @aborted
+
         @model
       end
 
       def action_request
         key = { @model_class.hash_key => @model.hash_key }
         key[@model_class.range_key] = @model.range_value if @model_class.range_key?
-        result = {
+        {
           delete: {
             key: key,
             table_name: @model_class.table_name
           }
         }
-        result
       end
 
       private
diff --git a/lib/dynamoid/transaction_write/save.rb b/lib/dynamoid/transaction_write/save.rb
index c5e1658e..b5ee221b 100644
--- a/lib/dynamoid/transaction_write/save.rb
+++ b/lib/dynamoid/transaction_write/save.rb
@@ -16,14 +16,12 @@ def initialize(model, **options)
       def on_registration
         validate_model!
 
-        unless @options[:validate] == false
-          unless @valid = @model.valid?
-            if @options[:raise_error]
-              raise Dynamoid::Errors::DocumentNotValid, @model
-            else
-              @aborted = true
-              return
-            end
+        if @options[:validate] != false && !(@valid = @model.valid?)
+          if @options[:raise_error]
+            raise Dynamoid::Errors::DocumentNotValid, @model
+          else
+            @aborted = true
+            return
           end
         end
 
@@ -143,8 +141,6 @@ def action_request_to_update
         result
       end
 
-      private
-
       def touch_model_timestamps(skip_created_at:)
         return unless @model_class.timestamps_enabled?
 
diff --git a/lib/dynamoid/transaction_write/update_fields.rb b/lib/dynamoid/transaction_write/update_fields.rb
index 8505d823..c25295ce 100644
--- a/lib/dynamoid/transaction_write/update_fields.rb
+++ b/lib/dynamoid/transaction_write/update_fields.rb
@@ -14,8 +14,7 @@ def on_registration
         validate_primary_key!
       end
 
-      def on_completing
-      end
+      def on_completing; end
 
       def aborted?
         false
diff --git a/lib/dynamoid/transaction_write/upsert.rb b/lib/dynamoid/transaction_write/upsert.rb
index a4a00c6f..acdb9724 100644
--- a/lib/dynamoid/transaction_write/upsert.rb
+++ b/lib/dynamoid/transaction_write/upsert.rb
@@ -14,8 +14,7 @@ def on_registration
         validate_primary_key!
       end
 
-      def on_completing
-      end
+      def on_completing; end
 
       def aborted?
         false
@@ -54,7 +53,7 @@ def action_request
         # expression_attribute_names = attribute_keys_in_model.map{|k| ["##{k}","#{k}"]}.to_h
         expression_attribute_names.merge!(item_keys.each_with_index.map { |k, i| ["#_n#{i}", k.to_s] }.to_h)
 
-        result = {
+        {
           update: {
             key: key,
             table_name: @model_class.table_name,
@@ -63,8 +62,6 @@ def action_request
             expression_attribute_values: expression_attribute_values
           }
         }
-
-        result
       end
 
       private
diff --git a/spec/dynamoid/persistence_spec.rb b/spec/dynamoid/persistence_spec.rb
index 29a8ac1e..58356a57 100644
--- a/spec/dynamoid/persistence_spec.rb
+++ b/spec/dynamoid/persistence_spec.rb
@@ -871,17 +871,17 @@ def around_save_callback
         end
 
         klass_with_callbacks.create!
-        expect(ScratchPad.recorded).to eql [ # rubocop:disable Style/StringConcatenation
-                                             'run before_validation',
-                                             'run after_validation',
-                                             'run before_save',
-                                             'start around_save',
-                                             'run before_create',
-                                             'start around_create',
-                                             'finish around_create',
-                                             'run after_create',
-                                             'finish around_save',
-                                             'run after_save'
+        expect(ScratchPad.recorded).to eql [
+          'run before_validation',
+          'run after_validation',
+          'run before_save',
+          'start around_save',
+          'run before_create',
+          'start around_create',
+          'finish around_create',
+          'run after_create',
+          'finish around_save',
+          'run after_save'
         ]
       end
     end
@@ -2010,7 +2010,7 @@ def around_update_callback
       }.to('[Updated]')
     end
 
-    # TODO:
+    # TODO: implement the test later
     # it 'raises ...Error when range key is missing'
 
     # TODO: add this case for save/save! and update_attributes/other update operations
diff --git a/spec/dynamoid/transaction_write/commit_spec.rb b/spec/dynamoid/transaction_write/commit_spec.rb
index 8b6bcf52..bc6948d2 100644
--- a/spec/dynamoid/transaction_write/commit_spec.rb
+++ b/spec/dynamoid/transaction_write/commit_spec.rb
@@ -15,6 +15,6 @@
     transaction.create klass
     transaction.create klass
 
-    expect { transaction.commit }.to change { klass.count }.by(2)
+    expect { transaction.commit }.to change(klass, :count).by(2)
   end
 end
diff --git a/spec/dynamoid/transaction_write/create_spec.rb b/spec/dynamoid/transaction_write/create_spec.rb
index 26975fde..bf359fa0 100644
--- a/spec/dynamoid/transaction_write/create_spec.rb
+++ b/spec/dynamoid/transaction_write/create_spec.rb
@@ -2,7 +2,7 @@
 
 require 'spec_helper'
 
-describe Dynamoid::TransactionWrite, '.create' do
+describe Dynamoid::TransactionWrite, '.create' do # rubocop:disable RSpec/MultipleDescribes
   let(:klass) do
     new_class do
       field :name
@@ -57,7 +57,7 @@ def around_save_callback
       described_class.execute do |txn|
         txn.create klass, name: 'Alex'
       end
-    }.to change { klass.count }.by(1)
+    }.to change(klass, :count).by(1)
 
     obj = klass.last
     expect(obj.name).to eql 'Alex'
@@ -84,7 +84,7 @@ def around_save_callback
       described_class.execute do |txn|
         result = txn.create klass, [{ name: 'Alex' }, { name: 'Michael' }]
       end
-    }.to change { klass.count }.by(2)
+    }.to change(klass, :count).by(2)
 
     expect(klass.pluck(:name)).to contain_exactly('Alex', 'Michael')
     expect(result.size).to eq 2
@@ -100,7 +100,7 @@ def around_save_callback
 
       described_class.execute do |txn|
         obj = txn.create klass, { name: 'Alex' } do |u|
-          u.name += " [Updated]"
+          u.name += ' [Updated]'
         end
       end
 
@@ -113,7 +113,7 @@ def around_save_callback
 
       described_class.execute do |txn|
         objects = txn.create klass, [{ name: 'Alex' }, { name: 'Michael' }] do |u|
-          u.name += " [Updated]"
+          u.name += ' [Updated]'
         end
       end
 
@@ -121,7 +121,7 @@ def around_save_callback
     end
   end
 
-  # TODO:
+  # TODO: implement the test later
   it 'can be called without attributes to modify'
 
   describe 'primary key schema' do
@@ -133,7 +133,7 @@ def around_save_callback
           described_class.execute do |txn|
             txn.create klass, name: 'Alex'
           end
-        }.to change { klass.count }.by(1)
+        }.to change(klass, :count).by(1)
       end
     end
 
@@ -145,7 +145,7 @@ def around_save_callback
           described_class.execute do |txn|
             txn.create klass_with_composite_key, name: 'Alex', age: 3
           end
-        }.to change { klass_with_composite_key.count }.by(1)
+        }.to change(klass_with_composite_key, :count).by(1)
       end
     end
   end
@@ -226,7 +226,7 @@ def around_save_callback
         described_class.execute do |txn|
           obj = txn.create(klass_with_validation, name: 'oneone')
         end
-      }.to change { klass_with_validation.count }.by(1)
+      }.to change(klass_with_validation, :count).by(1)
 
       expect(obj).to be_persisted
       expect(obj).not_to be_changed
@@ -239,7 +239,7 @@ def around_save_callback
         described_class.execute do |txn|
           obj = txn.create(klass_with_validation, name: 'one')
         end
-      }.not_to change { klass_with_validation.count }
+      }.not_to change(klass_with_validation, :count)
 
       expect(obj).not_to be_persisted
       expect(obj).to be_changed
@@ -253,7 +253,7 @@ def around_save_callback
 
       expect(obj).to be_a(klass_with_validation)
       expect(obj.name).to eql 'one'
-      expect(obj).to_not be_persisted
+      expect(obj).not_to be_persisted
     end
 
     it 'does not roll back the whole transaction when a model to be created is invalid' do
@@ -265,9 +265,9 @@ def around_save_callback
           obj_invalid = txn.create(klass_with_validation, name: 'one')
           obj_valid = txn.create(klass_with_validation, name: 'twotwo')
         end
-      }.to change { klass_with_validation.count }.by(1)
+      }.to change(klass_with_validation, :count).by(1)
 
-      expect(obj_invalid).to_not be_persisted
+      expect(obj_invalid).not_to be_persisted
       expect(obj_valid).to be_persisted
 
       obj_valid_loaded = klass_with_validation.find(obj_valid.id)
@@ -348,9 +348,9 @@ def around_save_callback
     expect {
       described_class.execute do |txn|
         obj = txn.create klass, name: 'Alex'
-        raise "trigger rollback"
+        raise 'trigger rollback'
       end
-    }.to raise_error("trigger rollback")
+    }.to raise_error('trigger rollback')
 
     expect(obj).not_to be_persisted
     expect(obj).to be_changed
@@ -485,17 +485,17 @@ def around_save_callback
         txn.create klass_with_all_callbacks
       end
 
-      expect(ScratchPad.recorded).to eql [ # rubocop:disable Style/StringConcatenation
-                                           'run before_validation',
-                                           'run after_validation',
-                                           'run before_save',
-                                           'start around_save',
-                                           'run before_create',
-                                           'start around_create',
-                                           'finish around_create',
-                                           'run after_create',
-                                           'finish around_save',
-                                           'run after_save'
+      expect(ScratchPad.recorded).to eql [
+        'run before_validation',
+        'run after_validation',
+        'run before_save',
+        'start around_save',
+        'run before_create',
+        'start around_create',
+        'finish around_create',
+        'run after_create',
+        'finish around_save',
+        'run after_save'
       ]
     end
 
@@ -520,7 +520,8 @@ def around_save_callback
         'finish around_create',
         'run after_create',
         'finish around_save',
-        'run after_save')
+        'run after_save'
+      )
       expect(ScratchPad.recorded).to eql []
     end
   end
@@ -547,7 +548,7 @@ def around_save_callback
       described_class.execute do |txn|
         txn.create! klass, name: 'Alex'
       end
-    }.to change { klass.count }.by(1)
+    }.to change(klass, :count).by(1)
 
     obj = klass.last
     expect(obj.name).to eql 'Alex'
@@ -574,7 +575,7 @@ def around_save_callback
       described_class.execute do |txn|
         result = txn.create! klass, [{ name: 'Alex' }, { name: 'Michael' }]
       end
-    }.to change { klass.count }.by(2)
+    }.to change(klass, :count).by(2)
 
     expect(klass.pluck(:name)).to contain_exactly('Alex', 'Michael')
     expect(result.size).to eq 2
@@ -590,7 +591,7 @@ def around_save_callback
 
       described_class.execute do |txn|
         obj = txn.create! klass, { name: 'Alex' } do |u|
-          u.name += " [Updated]"
+          u.name += ' [Updated]'
         end
       end
 
@@ -603,7 +604,7 @@ def around_save_callback
 
       described_class.execute do |txn|
         objects = txn.create! klass, [{ name: 'Alex' }, { name: 'Michael' }] do |u|
-          u.name += " [Updated]"
+          u.name += ' [Updated]'
         end
       end
 
@@ -623,7 +624,7 @@ def around_save_callback
         described_class.execute do |txn|
           obj = txn.create!(klass_with_validation, name: 'oneone')
         end
-      }.to change { klass_with_validation.count }.by(1)
+      }.to change(klass_with_validation, :count).by(1)
 
       expect(obj).to be_persisted
       expect(obj).not_to be_changed
@@ -645,7 +646,7 @@ def around_save_callback
             txn.create!(klass_with_validation, name: 'one')
           end
         }.to raise_error(Dynamoid::Errors::DocumentNotValid)
-      }.to_not change { klass_with_validation.count }
+      }.not_to change(klass_with_validation, :count)
     end
   end
 
diff --git a/spec/dynamoid/transaction_write/delete_spec.rb b/spec/dynamoid/transaction_write/delete_spec.rb
index 9c6858d0..83ddd1d5 100644
--- a/spec/dynamoid/transaction_write/delete_spec.rb
+++ b/spec/dynamoid/transaction_write/delete_spec.rb
@@ -2,7 +2,7 @@
 
 require 'spec_helper'
 
-describe Dynamoid::TransactionWrite, '#delete(model)' do
+describe Dynamoid::TransactionWrite, '#delete(model)' do # rubocop:disable RSpec/MultipleDescribes
   let(:klass) do
     new_class do
       field :name
@@ -23,7 +23,7 @@
       described_class.execute do |txn|
         txn.delete obj
       end
-    }.to change { klass.count }.by(-1)
+    }.to change(klass, :count).by(-1)
 
     expect(klass.exists?(obj.id)).to eql false
     expect(obj).to be_destroyed
@@ -49,7 +49,7 @@
           described_class.execute do |txn|
             txn.delete obj
           end
-        }.to change { klass.count }.by(-1)
+        }.to change(klass, :count).by(-1)
       end
     end
 
@@ -61,7 +61,7 @@
           described_class.execute do |txn|
             txn.delete obj
           end
-        }.to change { klass_with_composite_key.count }.by(-1)
+        }.to change(klass_with_composite_key, :count).by(-1)
       end
     end
   end
@@ -130,9 +130,9 @@
     expect {
       described_class.execute do |txn|
         txn.delete obj
-        raise "trigger rollback"
+        raise 'trigger rollback'
       end
-    }.to raise_error("trigger rollback")
+    }.to raise_error('trigger rollback')
 
     expect(obj).not_to be_destroyed
   end
@@ -208,7 +208,7 @@ def around_destroy_callback
       described_class.execute do |txn|
         txn.delete klass, obj.id
       end
-    }.to change { klass.count }.by(-1)
+    }.to change(klass, :count).by(-1)
 
     expect(klass.exists?(obj.id)).to eql false
   end
@@ -233,7 +233,7 @@ def around_destroy_callback
           described_class.execute do |txn|
             txn.delete klass, obj.id
           end
-        }.to change { klass.count }.by(-1)
+        }.to change(klass, :count).by(-1)
       end
     end
 
@@ -245,7 +245,7 @@ def around_destroy_callback
           described_class.execute do |txn|
             txn.delete klass_with_composite_key, obj.id, obj.age
           end
-        }.to change { klass_with_composite_key.count }.by(-1)
+        }.to change(klass_with_composite_key, :count).by(-1)
       end
 
       it 'raises MissingHashKey if partition key is not specified' do
diff --git a/spec/dynamoid/transaction_write/destroy_spec.rb b/spec/dynamoid/transaction_write/destroy_spec.rb
index 256f4e44..fa0147dc 100644
--- a/spec/dynamoid/transaction_write/destroy_spec.rb
+++ b/spec/dynamoid/transaction_write/destroy_spec.rb
@@ -2,7 +2,7 @@
 
 require 'spec_helper'
 
-describe Dynamoid::TransactionWrite, '#destroy' do
+describe Dynamoid::TransactionWrite, '#destroy' do # rubocop:disable RSpec/MultipleDescribes
   let(:klass) do
     new_class do
       field :name
@@ -37,7 +37,7 @@ def around_destroy_callback
       described_class.execute do |txn|
         txn.destroy obj
       end
-    }.to change { klass.count }.by(-1)
+    }.to change(klass, :count).by(-1)
 
     expect(klass.exists?(obj.id)).to eql false
     expect(obj).to be_destroyed
@@ -63,7 +63,7 @@ def around_destroy_callback
           described_class.execute do |txn|
             txn.destroy obj
           end
-        }.to change { klass.count }.by(-1)
+        }.to change(klass, :count).by(-1)
       end
     end
 
@@ -75,7 +75,7 @@ def around_destroy_callback
           described_class.execute do |txn|
             txn.destroy obj
           end
-        }.to change { klass_with_composite_key.count }.by(-1)
+        }.to change(klass_with_composite_key, :count).by(-1)
       end
     end
   end
@@ -130,7 +130,7 @@ def around_destroy_callback
           txn.destroy obj_to_destroy
           txn.save obj_to_save
         end
-      }.to change { klass.count }.by(1)
+      }.to change(klass, :count).by(1)
 
       expect(obj_to_destroy).to be_destroyed
       expect(obj_to_save).to be_persisted
@@ -190,9 +190,9 @@ def around_destroy_callback
     expect {
       described_class.execute do |txn|
         txn.destroy obj
-        raise "trigger rollback"
+        raise 'trigger rollback'
       end
-    }.to raise_error("trigger rollback")
+    }.to raise_error('trigger rollback')
 
     expect(obj).not_to be_destroyed
   end
@@ -256,11 +256,11 @@ def around_destroy_callback
         txn.destroy obj
       end
 
-      expect(ScratchPad.recorded).to eql [ # rubocop:disable Style/StringConcatenation
-                                           'run before_destroy',
-                                           'start around_destroy',
-                                           'finish around_destroy',
-                                           'run after_destroy'
+      expect(ScratchPad.recorded).to eql [
+        'run before_destroy',
+        'start around_destroy',
+        'finish around_destroy',
+        'run after_destroy'
       ]
     end
 
@@ -280,7 +280,8 @@ def around_destroy_callback
         'run before_destroy',
         'start around_destroy',
         'finish around_destroy',
-        'run after_destroy')
+        'run after_destroy'
+      )
       expect(ScratchPad.recorded).to eql []
     end
 
@@ -318,7 +319,7 @@ def around_destroy_callback
       described_class.execute do |txn|
         txn.destroy! obj
       end
-    }.to change { klass.count }.by(-1)
+    }.to change(klass, :count).by(-1)
 
     expect(klass.exists?(obj.id)).to eql false
   end
@@ -367,7 +368,7 @@ def around_destroy_callback
         txn.destroy! obj_to_destroy
         txn.save obj_to_save
       end
-    }.to change { klass.count }.by(1)
+    }.to change(klass, :count).by(1)
 
     expect(obj_to_destroy).to be_destroyed
     expect(obj_to_save).to be_persisted
diff --git a/spec/dynamoid/transaction_write/save_spec.rb b/spec/dynamoid/transaction_write/save_spec.rb
index 15138abd..a85aff1b 100644
--- a/spec/dynamoid/transaction_write/save_spec.rb
+++ b/spec/dynamoid/transaction_write/save_spec.rb
@@ -2,7 +2,7 @@
 
 require 'spec_helper'
 
-describe Dynamoid::TransactionWrite, '.save' do
+describe Dynamoid::TransactionWrite, '.save' do # rubocop:disable RSpec/MultipleDescribes
   let(:klass) do
     new_class do
       field :name
@@ -70,7 +70,7 @@ def around_save_callback
       described_class.execute do |txn|
         txn.save obj
       end
-    }.to change { klass.count }.by(1)
+    }.to change(klass, :count).by(1)
 
     obj_loaded = klass.find(obj.id)
     expect(obj_loaded.name).to eql 'Alex'
@@ -115,7 +115,7 @@ def around_save_callback
           described_class.execute do |txn|
             txn.save obj
           end
-        }.to change { klass.count }.by(1)
+        }.to change(klass, :count).by(1)
       end
 
       it 'persists changes in already persisted model' do
@@ -139,7 +139,7 @@ def around_save_callback
           described_class.execute do |txn|
             txn.save obj
           end
-        }.to change { klass_with_composite_key.count }.by(1)
+        }.to change(klass_with_composite_key, :count).by(1)
       end
 
       it 'persists changes in already persisted model' do
@@ -383,7 +383,7 @@ def around_save_callback
           described_class.execute do |txn|
             txn.save obj
           end
-        }.not_to change { klass_with_validation.count }
+        }.not_to change(klass_with_validation, :count)
 
         expect(obj).not_to be_persisted
         expect(obj).to be_changed
@@ -398,7 +398,7 @@ def around_save_callback
             described_class.execute do |txn|
               txn.save obj, validate: false
             end
-          }.to change { klass_with_validation.count }.by(1)
+          }.to change(klass_with_validation, :count).by(1)
 
           obj_loaded = klass_with_validation.find(obj.id)
           expect(obj_loaded.name).to eql 'one'
@@ -444,7 +444,7 @@ def around_save_callback
             txn.save obj_invalid
             txn.save obj_valid
           end
-        }.to change { klass_with_validation.count }.by(1)
+        }.to change(klass_with_validation, :count).by(1)
 
         expect(klass_with_validation.all.map(&:id)).to contain_exactly(obj_valid.id)
       end
@@ -476,7 +476,7 @@ def around_save_callback
           described_class.execute do |txn|
             txn.save obj
           end
-        }.not_to change { klass_with_validation.count }
+        }.not_to change(klass_with_validation, :count)
 
         expect(obj).to be_persisted
         expect(obj).to be_changed
@@ -680,11 +680,11 @@ def around_save_callback
     obj_to_create = nil
 
     expect {
-        described_class.execute do |txn|
-          txn.save obj_deleted
-          obj_to_create = txn.create klass, name: 'two'
-        end
-    }.to change { klass.count }.by(2)
+      described_class.execute do |txn|
+        txn.save obj_deleted
+        obj_to_create = txn.create klass, name: 'two'
+      end
+    }.to change(klass, :count).by(2)
 
     expect(obj_to_create).to be_persisted
     expect(obj_to_create).not_to be_changed
@@ -696,9 +696,9 @@ def around_save_callback
     expect {
       described_class.execute do |txn|
         txn.save obj
-        raise "trigger rollback"
+        raise 'trigger rollback'
       end
-    }.to raise_error("trigger rollback")
+    }.to raise_error('trigger rollback')
 
     expect(obj).not_to be_persisted
     expect(obj).to be_changed
@@ -711,9 +711,9 @@ def around_save_callback
     expect {
       described_class.execute do |txn|
         txn.save obj
-        raise "trigger rollback"
+        raise 'trigger rollback'
       end
-    }.to raise_error("trigger rollback")
+    }.to raise_error('trigger rollback')
 
     expect(obj).to be_changed
   end
@@ -867,17 +867,17 @@ def around_create_callback
           txn.save obj
         end
 
-        expect(ScratchPad.recorded).to eql [ # rubocop:disable Style/StringConcatenation
-                            'run before_validation',
-                            'run after_validation',
-                            'run before_save',
-                            'start around_save',
-                            'run before_create',
-                            'start around_create',
-                            'finish around_create',
-                            'run after_create',
-                            'finish around_save',
-                            'run after_save'
+        expect(ScratchPad.recorded).to eql [
+          'run before_validation',
+          'run after_validation',
+          'run before_save',
+          'start around_save',
+          'run before_create',
+          'start around_create',
+          'finish around_create',
+          'run after_create',
+          'finish around_save',
+          'run after_save'
         ]
       end
 
@@ -903,7 +903,8 @@ def around_create_callback
           'finish around_create',
           'run after_create',
           'finish around_save',
-          'run after_save')
+          'run after_save'
+        )
         expect(ScratchPad.recorded).to eql []
       end
 
@@ -1098,17 +1099,17 @@ def around_update_callback
           txn.save obj
         end
 
-        expect(ScratchPad.recorded).to eql [ # rubocop:disable Style/StringConcatenation
-                                             'run before_validation',
-                                             'run after_validation',
-                                             'run before_save',
-                                             'start around_save',
-                                             'run before_update',
-                                             'start around_update',
-                                             'finish around_update',
-                                             'run after_update',
-                                             'finish around_save',
-                                             'run after_save'
+        expect(ScratchPad.recorded).to eql [
+          'run before_validation',
+          'run after_validation',
+          'run before_save',
+          'start around_save',
+          'run before_update',
+          'start around_update',
+          'finish around_update',
+          'run after_update',
+          'finish around_save',
+          'run after_save'
         ]
       end
 
@@ -1135,7 +1136,8 @@ def around_update_callback
           'finish around_update',
           'run after_update',
           'finish around_save',
-          'run after_save')
+          'run after_save'
+        )
         expect(ScratchPad.recorded).to eql []
       end
     end
@@ -1164,7 +1166,7 @@ def around_update_callback
       described_class.execute do |txn|
         txn.save! obj
       end
-    }.to change { klass.count }.by(1)
+    }.to change(klass, :count).by(1)
 
     obj_loaded = klass.find(obj.id)
     expect(obj_loaded.name).to eql 'Alex'
@@ -1221,7 +1223,7 @@ def around_update_callback
         described_class.execute do |txn|
           txn.save! obj, validate: false
         end
-      }.to change { klass_with_validation.count }.by(1)
+      }.to change(klass_with_validation, :count).by(1)
 
       obj_loaded = klass_with_validation.find(obj.id)
       expect(obj_loaded.name).to eql 'one'
@@ -1244,7 +1246,7 @@ def around_update_callback
             txn.save! obj_invalid
           end
         }.to raise_error(Dynamoid::Errors::DocumentNotValid)
-      }.not_to change { klass_with_validation.count }
+      }.not_to change(klass_with_validation, :count)
     end
 
     it 'rolls back the whole transaction when a model to be saved is invalid' do
@@ -1393,7 +1395,7 @@ def around_update_callback
           obj_to_create = txn.create klass, name: 'Michael'
         end
       }.to raise_error(Aws::DynamoDB::Errors::TransactionCanceledException)
-    }.not_to change { klass.count }
+    }.not_to change(klass, :count)
 
     expect(klass.count).to eql 1
     expect(klass.all.to_a).to eql [existing]
diff --git a/spec/dynamoid/transaction_write/update_attributes_spec.rb b/spec/dynamoid/transaction_write/update_attributes_spec.rb
index 5687300c..a4b2f040 100644
--- a/spec/dynamoid/transaction_write/update_attributes_spec.rb
+++ b/spec/dynamoid/transaction_write/update_attributes_spec.rb
@@ -2,7 +2,7 @@
 
 require 'spec_helper'
 
-describe Dynamoid::TransactionWrite, '#update_attributes' do
+describe Dynamoid::TransactionWrite, '#update_attributes' do # rubocop:disable RSpec/MultipleDescribes
   let(:klass) do
     new_class do
       field :name
@@ -64,10 +64,10 @@ def around_save_callback
     expect(obj.changed?).to eql false
   end
 
-  # TODO:
+  # TODO: implement the test later
   it 'raises exception if a model is not persisted'
 
-  # TODO:
+  # TODO: implement the test later
   it 'can be called without attributes to modify'
 
   describe 'primary key schema' do
@@ -308,7 +308,7 @@ def around_save_callback
         txn.update_attributes obj_deleted, name: 'Alex [Updated]'
         obj_to_create = txn.create klass, name: 'Michael'
       end
-    }.to change { klass.count }.by(2)
+    }.to change(klass, :count).by(2)
 
     expect(obj_to_create).to be_persisted
     expect(obj_deleted).to be_persisted
@@ -322,9 +322,9 @@ def around_save_callback
     expect {
       described_class.execute do |txn|
         txn.update_attributes obj, name: 'Alex [Updated]'
-        raise "trigger rollback"
+        raise 'trigger rollback'
       end
-    }.to raise_error("trigger rollback")
+    }.to raise_error('trigger rollback')
 
     expect(obj).to be_changed
   end
@@ -474,17 +474,17 @@ def around_update_callback
         txn.update_attributes obj, name: 'Bob'
       end
 
-      expect(ScratchPad.recorded).to eql [ # rubocop:disable Style/StringConcatenation
-                                           'run before_validation',
-                                           'run after_validation',
-                                           'run before_save',
-                                           'start around_save',
-                                           'run before_update',
-                                           'start around_update',
-                                           'finish around_update',
-                                           'run after_update',
-                                           'finish around_save',
-                                           'run after_save'
+      expect(ScratchPad.recorded).to eql [
+        'run before_validation',
+        'run after_validation',
+        'run before_save',
+        'start around_save',
+        'run before_update',
+        'start around_update',
+        'finish around_update',
+        'run after_update',
+        'finish around_save',
+        'run after_save'
       ]
     end
 
@@ -592,17 +592,6 @@ def around_update_callback
       expect(result).to eql true
     end
 
-    it 'returns true when model valid' do
-      obj = klass_with_validation.create!(name: 'oneone')
-
-      result = nil
-      described_class.execute do |txn|
-        result = txn.update_attributes!(obj, name: 'oneone [Updated]')
-      end
-
-      expect(result).to eql true
-    end
-
     it 'raise DocumentNotValid when model invalid' do
       obj = klass_with_validation.create!(name: 'oneone')
 
@@ -686,7 +675,7 @@ def around_update_callback
         txn.update_attributes! obj_deleted, name: 'Alex [Updated]'
         obj_to_create = txn.create klass, name: 'Michael'
       end
-    }.to change { klass.count }.by(2)
+    }.to change(klass, :count).by(2)
 
     expect(obj_to_create).to be_persisted
     expect(obj_deleted).to be_persisted
diff --git a/spec/dynamoid/transaction_write/update_fields_spec.rb b/spec/dynamoid/transaction_write/update_fields_spec.rb
index 75afcb0d..96289074 100644
--- a/spec/dynamoid/transaction_write/update_fields_spec.rb
+++ b/spec/dynamoid/transaction_write/update_fields_spec.rb
@@ -28,7 +28,7 @@
     expect(obj).not_to be_changed
   end
 
-  # TODO:
+  # TODO: implement the test later
   it 'can be called without attributes to modify'
 
   it 'returns nil' do
diff --git a/spec/dynamoid/transaction_write/upsert_spec.rb b/spec/dynamoid/transaction_write/upsert_spec.rb
index d968323d..88290301 100644
--- a/spec/dynamoid/transaction_write/upsert_spec.rb
+++ b/spec/dynamoid/transaction_write/upsert_spec.rb
@@ -26,7 +26,7 @@
       described_class.execute do |txn|
         txn.upsert klass, id_new, name: 'Alex'
       end
-    }.to change { klass.count }.by(1)
+    }.to change(klass, :count).by(1)
 
     obj = klass.find(id_new)
     expect(obj.name).to eql 'Alex'
@@ -74,7 +74,7 @@
           described_class.execute do |txn|
             txn.upsert klass, id_new, {}
           end
-        }.to change { klass.count }.by(1)
+        }.to change(klass, :count).by(1)
       end
 
       it 'persists changes in already persisted model' do
@@ -97,7 +97,7 @@
           described_class.execute do |txn|
             txn.upsert klass_with_composite_key, id_new, 3, {}
           end
-        }.to change { klass_with_composite_key.count }.by(1)
+        }.to change(klass_with_composite_key, :count).by(1)
       end
 
       it 'persists changes in already persisted model' do
diff --git a/spec/dynamoid/type_casting_spec.rb b/spec/dynamoid/type_casting_spec.rb
index 38b91a82..9abb4964 100644
--- a/spec/dynamoid/type_casting_spec.rb
+++ b/spec/dynamoid/type_casting_spec.rb
@@ -274,7 +274,7 @@
 
         obj = klass.new(values: Set.new([1, 1.5, '2'.to_d]))
 
-        expect(obj.values).to eql(Set.new([1, 1, 2]))
+        expect(obj.values).to eql(Set.new([1, 2]))
       end
 
       it 'type casts numbers' do
diff --git a/spec/support/scratch_pad.rb b/spec/support/scratch_pad.rb
index 5c73f318..cb2ca516 100644
--- a/spec/support/scratch_pad.rb
+++ b/spec/support/scratch_pad.rb
@@ -35,4 +35,3 @@ def self.inspect
     "<ScratchPad @record=#{@record.inspect}>"
   end
 end
-