diff --git a/app/models/spree/adjustment.rb b/app/models/spree/adjustment.rb
index 37de2b20df..975fc82201 100644
--- a/app/models/spree/adjustment.rb
+++ b/app/models/spree/adjustment.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'spree/localized_number'
 require 'concerns/adjustment_scopes'
 
@@ -97,6 +99,7 @@ module Spree
     # Should return _true_ if originator is absent or doesn't implement _eligible?_
     def eligible_for_originator?
       return true if originator.nil?
+
       !originator.respond_to?(:eligible?) || originator.eligible?(source)
     end
 
@@ -109,13 +112,14 @@ module Spree
     # are not recalculated.
     #
     # It receives +calculable+ as the updated source here so calculations can be
-    # performed on the current values of that source. If we used +source+ it 
+    # performed on the current values of that source. If we used +source+ it
     # could load the old record from db for the association. e.g. when updating
     # more than on line items at once via accepted_nested_attributes the order
     # object on the association would be in a old state and therefore the
     # adjustment calculations would not performed on proper values
     def update!(calculable = nil)
       return if immutable?
+
       # Fix for #3381
       # If we attempt to call 'source' before the reload, then source is currently
       # the order object. After calling a reload, the source is the Shipment.
@@ -171,8 +175,8 @@ module Spree
 
     private
 
-      def update_adjustable
-        adjustable.update! if adjustable.is_a? Order
-      end
+    def update_adjustable
+      adjustable.update! if adjustable.is_a? Order
+    end
   end
 end
diff --git a/app/models/spree/calculator.rb b/app/models/spree/calculator.rb
index 4ce5b53c13..40bea838f5 100644
--- a/app/models/spree/calculator.rb
+++ b/app/models/spree/calculator.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Spree
   class Calculator < ActiveRecord::Base
     belongs_to :calculable, polymorphic: true
@@ -5,7 +7,7 @@ module Spree
     # This method must be overriden in concrete calculator.
     #
     # It should return amount computed based on #calculable and/or optional parameter
-    def compute(something = nil)
+    def compute(_something = nil)
       raise NotImplementedError, 'please use concrete calculator'
     end
 
@@ -16,8 +18,7 @@ module Spree
 
     ###################################################################
 
-    def self.register(*klasses)
-    end
+    def self.register(*klasses); end
 
     # Returns all calculators applicable for kind of work
     def self.calculators
@@ -32,7 +33,7 @@ module Spree
       self.class.description
     end
 
-    def available?(object)
+    def available?(_object)
       true
     end
 
diff --git a/app/models/spree/tax_category.rb b/app/models/spree/tax_category.rb
index 6e0dd27da1..7bcad54fe7 100644
--- a/app/models/spree/tax_category.rb
+++ b/app/models/spree/tax_category.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Spree
   class TaxCategory < ActiveRecord::Base
     acts_as_paranoid
@@ -8,7 +10,7 @@ module Spree
     before_save :set_default_category
 
     def set_default_category
-      #set existing default tax category to false if this one has been marked as default
+      # set existing default tax category to false if this one has been marked as default
 
       if is_default && tax_category = self.class.where(is_default: true).first
         tax_category.update_column(:is_default, false) unless tax_category == self
diff --git a/app/models/spree/tax_rate.rb b/app/models/spree/tax_rate.rb
index d31345e0da..d7dd93db8f 100644
--- a/app/models/spree/tax_rate.rb
+++ b/app/models/spree/tax_rate.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Spree
   class DefaultTaxZoneValidator < ActiveModel::Validator
     def validate(record)
@@ -35,7 +37,7 @@ module Spree
       order.adjustments.tax.destroy_all
       order.line_item_adjustments.where(originator_type: 'Spree::TaxRate').destroy_all
 
-      self.match(order).each do |rate|
+      match(order).each do |rate|
         rate.adjust(order)
       end
     end
@@ -104,11 +106,11 @@ module Spree
 
     private
 
-      def create_label
-        label = ""
-        label << (name.present? ? name : tax_category.name) + " "
-        label << (show_rate_in_label? ? "#{amount * 100}%" : "")
-      end
+    def create_label
+      label = ""
+      label << (name.presence || tax_category.name) + " "
+      label << (show_rate_in_label? ? "#{amount * 100}%" : "")
+    end
 
     def with_tax_included_in_price
       old_included_in_price = included_in_price
diff --git a/spec/models/spree/adjustment_spec.rb b/spec/models/spree/adjustment_spec.rb
index 123ece3534..2eec4943c7 100644
--- a/spec/models/spree/adjustment_spec.rb
+++ b/spec/models/spree/adjustment_spec.rb
@@ -3,7 +3,7 @@ require 'spec_helper'
 module Spree
   describe Adjustment do
     let(:order) { mock_model(Spree::Order, update!: nil) }
-    let(:adjustment) { Spree::Adjustment.create(:label => "Adjustment", :amount => 5) }
+    let(:adjustment) { Spree::Adjustment.create(label: "Adjustment", amount: 5) }
 
     describe "scopes" do
       let!(:arbitrary_adjustment) { create(:adjustment, source: nil, label: "Arbitrary") }
@@ -104,9 +104,9 @@ module Spree
     context "#save" do
       it "should call order#update!" do
         adjustment = Spree::Adjustment.new(
-          :adjustable => order,
-          :amount => 10,
-          :label => "Foo"
+          adjustable: order,
+          amount: 10,
+          label: "Foo"
         )
         order.should_receive(:update!)
         adjustment.save
diff --git a/spec/models/spree/tax_category_spec.rb b/spec/models/spree/tax_category_spec.rb
index ea2c329aea..4ae82eb02d 100644
--- a/spec/models/spree/tax_category_spec.rb
+++ b/spec/models/spree/tax_category_spec.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'spec_helper'
 
 describe Spree::TaxCategory do
@@ -10,7 +12,7 @@ describe Spree::TaxCategory do
     end
 
     it "should undefault the previous default tax category" do
-      new_tax_category.update_attributes({:is_default => true})
+      new_tax_category.update({ is_default: true })
       new_tax_category.is_default.should be_true
 
       tax_category.reload