diff --git a/ancestry.gemspec b/ancestry.gemspec
index d2c9b880..388a2e03 100644
--- a/ancestry.gemspec
+++ b/ancestry.gemspec
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 lib = File.expand_path('../lib/', __FILE__)
-$:.unshift lib unless $:.include?(lib)
+$LOAD_PATH.unshift(lib) unless $LOAD_PATH.include?(lib)
 require 'ancestry/version'
 
 Gem::Specification.new do |s|
@@ -24,6 +24,7 @@ EOF
     "changelog_uri" => "https://github.com/stefankroes/ancestry/blob/master/CHANGELOG.md",
     "source_code_uri" => "https://github.com/stefankroes/ancestry/",
     "bug_tracker_uri" => "https://github.com/stefankroes/ancestry/issues",
+    "rubygems_mfa_required" => "true"
   }
   s.version = Ancestry::VERSION
 
@@ -32,19 +33,19 @@ EOF
   s.homepage = 'https://github.com/stefankroes/ancestry'
   s.license  = 'MIT'
 
-  s.files = Dir[ 
+  s.files = Dir[
     "{lib}/**/*",
     'CHANGELOG.md',
     'MIT-LICENSE',
     'README.md'
   ]
   s.require_paths = ["lib"]
-  
-  s.required_ruby_version     = '>= 2.5'
+
+  s.required_ruby_version = '>= 2.5'
   s.add_runtime_dependency 'activerecord', '>= 5.2.6'
   s.add_development_dependency 'appraisal'
   s.add_development_dependency 'minitest'
-  s.add_development_dependency 'rake',      '~> 13.0'
+  s.add_development_dependency 'rake', '~> 13.0'
   s.add_development_dependency 'simplecov'
   s.add_development_dependency 'yard'
 end
diff --git a/test/concerns/arrangement_test.rb b/test/concerns/arrangement_test.rb
index fb967160..bc0b125d 100644
--- a/test/concerns/arrangement_test.rb
+++ b/test/concerns/arrangement_test.rb
@@ -8,7 +8,7 @@ def root_node(model)
   end
 
   def middle_node(model)
-    root_node(model).children.sort_by(&:id).first
+    root_node(model).children.min_by(&:id)
   end
 
   def leaf_node(model)
@@ -25,7 +25,7 @@ def assert_tree(arranged_nodes, size_at_depth)
       assert_equal size_at_depth[1], children.size
       assert_equal node.children.sort_by(&:id), children.keys.sort_by(&:id)
 
-      assert_tree(children, size_at_depth[1..-1])
+      assert_tree(children, size_at_depth[1..])
     end
   end
 
@@ -41,7 +41,7 @@ def assert_tree_path(arranged_nodes, expected_ids)
     arranged_nodes.each do |node, children|
       assert_equal expected_ids[0], node.id
 
-      assert_tree_path(children, expected_ids[1..-1])
+      assert_tree_path(children, expected_ids[1..])
     end
   end
 
@@ -133,20 +133,25 @@ def test_arrange_serializable
     AncestryTestDatabase.with_model :depth => 2, :width => 2 do |model, _roots|
       col = model.ancestry_column
       # materialized path 2 has a slash at the beginning and end
-      fmt = AncestryTestDatabase.materialized_path2? ? -> (a) { a ? "/#{a}/" : "/" } : -> (a) {a}
-      result = [{
-        col=>fmt[nil], "id"=>4, "children"=> [{
-          col=>fmt["4"], "id"=>6, "children" => []
-        }, {
-          col=>fmt["4"], "id"=>5, "children" => []
-        }]
-      }, {
-        col=>fmt[nil], "id"=>1, "children"=> [{
-          col=>fmt["1"], "id"=>3, "children"=>[]
+      fmt =
+        if AncestryTestDatabase.materialized_path2?
+          ->(a) { a ? "/#{a}/" : "/" }
+        else
+          ->(a) { a }
+        end
+      result = [
+        {
+          col => fmt[nil], "id" => 4, "children" => [
+            {col => fmt["4"], "id" => 6, "children" => []},
+            {col => fmt["4"], "id" => 5, "children" => []}
+          ]
         }, {
-          col=>fmt["1"], "id"=>2, "children"=>[]
-        }]
-      }]
+          col => fmt[nil], "id" => 1, "children" => [
+            {col => fmt["1"], "id" => 3, "children" => []},
+            {col => fmt["1"], "id" => 2, "children" => []}
+          ]
+        }
+      ]
 
       assert_equal model.arrange_serializable(order: "id desc"), result
     end
@@ -154,19 +159,19 @@ def test_arrange_serializable
 
   def test_arrange_serializable_with_block
     AncestryTestDatabase.with_model :depth => 2, :width => 2 do |model, _roots|
-      expected_result = [{
-        "id"=>4, "children"=>[{
-          "id"=>6
-        }, {
-          "id"=>5
-        }]
-      }, {
-        "id"=>1, "children"=> [{
-          "id"=>3
+      expected_result = [
+        {
+          "id" => 4, "children" => [
+            {"id" => 6},
+            {"id" => 5}
+          ]
         }, {
-          "id"=>2
-        }]
-      }]
+          "id" => 1, "children" => [
+            {"id" => 3},
+            {"id" => 2}
+          ]
+        }
+      ]
       result = model.arrange_serializable(order: "id desc") do |parent, children|
         out = {}
         out["id"] = parent.id
diff --git a/test/concerns/has_ancestry_test.rb b/test/concerns/has_ancestry_test.rb
index 2bd3bf47..3a46d06a 100644
--- a/test/concerns/has_ancestry_test.rb
+++ b/test/concerns/has_ancestry_test.rb
@@ -98,7 +98,7 @@ def test_setup_test_nodes
   end
 
   def test_primary_key_is_an_integer
-    AncestryTestDatabase.with_model(extra_columns: { string_id: :string }) do |model|
+    AncestryTestDatabase.with_model(extra_columns: {string_id: :string}) do |model|
       model.primary_key = :string_id
 
       assert !model.primary_key_is_an_integer?
diff --git a/test/concerns/hooks_test.rb b/test/concerns/hooks_test.rb
index d16c50c9..033f3a12 100644
--- a/test/concerns/hooks_test.rb
+++ b/test/concerns/hooks_test.rb
@@ -9,7 +9,6 @@ def test_has_ancestry_in_after_save
       :orphan_strategy => :adopt,
       :extra_columns => {:name => :string, :name_path => :string}
     ) do |model|
-
       model.class_eval do
         before_save :before_save_hook
 
@@ -35,9 +34,8 @@ def before_save_hook
 
   def test_update_descendants_with_changed_parent_value
     AncestryTestDatabase.with_model(
-      extra_columns: { name: :string, name_path: :string }
+      extra_columns: {name: :string, name_path: :string}
     ) do |model|
-
       model.class_eval do
         before_save :update_name_path
         # this example will only work if the name field is unique across all levels
@@ -78,9 +76,9 @@ def update_descendants_hook(descendants_clause, old_ancestry, new_ancestry)
       assert_equal("changed", m5.reload.name_path)
       assert_equal([m5.id], m2.reload.ancestor_ids)
       assert_equal("changed/child", m2.reload.name_path)
-      assert_equal([m5.id,m2.id], m3.reload.ancestor_ids)
+      assert_equal([m5.id, m2.id], m3.reload.ancestor_ids)
       assert_equal("changed/child/grandchild", m3.reload.name_path)
-      assert_equal([m5.id,m2.id,m3.id], m4.reload.ancestor_ids)
+      assert_equal([m5.id, m2.id, m3.id], m4.reload.ancestor_ids)
       assert_equal("changed/child/grandchild/grandchild's grand", m4.reload.name_path)
     end
   end
@@ -134,15 +132,16 @@ def before_hook
   # see f94b22ba https://github.com/stefankroes/ancestry/pull/263
   def test_node_creation_in_after_commit
     AncestryTestDatabase.with_model do |model|
-      children=[]
+      children = []
       model.instance_eval do
         attr_accessor :idx
-        self.after_commit do
-          children << self.children.create!(:idx => self.idx - 1) if self.idx > 0
+
+        after_commit do
+          children << self.children.create!(:idx => idx - 1) if idx > 0
         end
       end
       model.create!(:idx => 3)
-      assert_equal [1,2,3], children.first.ancestor_ids
+      assert_equal [1, 2, 3], children.first.ancestor_ids
     end
   end
 end
diff --git a/test/concerns/integrity_checking_and_restoration_test.rb b/test/concerns/integrity_checking_and_restoration_test.rb
index 5586f21e..474a66e4 100644
--- a/test/concerns/integrity_checking_and_restoration_test.rb
+++ b/test/concerns/integrity_checking_and_restoration_test.rb
@@ -51,7 +51,7 @@ def test_integrity_checking
     end
   end
 
-  def assert_integrity_restoration model
+  def assert_integrity_restoration(model)
     assert_raise Ancestry::AncestryIntegrityException do
       model.check_ancestry_integrity!
     end
@@ -59,8 +59,8 @@ def assert_integrity_restoration model
     assert_nothing_raised do
       model.check_ancestry_integrity!
     end
-    assert model.all.any? {|node| node.has_parent? }, "Expected some nodes not to be roots"
-    assert_equal model.count, model.roots.collect {|node| node.descendants.count + 1 }.sum
+    assert model.all.any?(&:has_parent?), "Expected some nodes not to be roots"
+    assert_equal model.count, model.roots.collect { |node| node.descendants.count + 1 }.sum
   end
 
   def test_integrity_restoration
diff --git a/test/concerns/materialized_path_test.rb b/test/concerns/materialized_path_test.rb
index 7179321a..9a2c1a38 100644
--- a/test/concerns/materialized_path_test.rb
+++ b/test/concerns/materialized_path_test.rb
@@ -16,23 +16,23 @@ def test_ancestry_column_values
 
       # saved
       node.save!
-      assert_ancestry node, nil, child: "#{node.id}"
+      assert_ancestry node, nil, child: node.id.to_s
 
       # changed
       node.ancestor_ids = [root.id]
-      assert_ancestry node, "#{root.id}", db: nil, child: "#{node.id}"
+      assert_ancestry node, root.id.to_s, db: nil, child: node.id.to_s
 
       # changed saved
       node.save!
-      assert_ancestry node, "#{root.id}", child: "#{root.id}/#{node.id}"
+      assert_ancestry node, root.id.to_s, child: "#{root.id}/#{node.id}"
 
       # reloaded
       node.reload
-      assert_ancestry node, "#{root.id}", child: "#{root.id}/#{node.id}"
+      assert_ancestry node, root.id.to_s, child: "#{root.id}/#{node.id}"
 
       # fresh node
       node = model.find(node.id)
-      assert_ancestry node, "#{root.id}", child: "#{root.id}/#{node.id}"
+      assert_ancestry node, root.id.to_s, child: "#{root.id}/#{node.id}"
     end
   end
 
diff --git a/test/concerns/orphan_strategies_test.rb b/test/concerns/orphan_strategies_test.rb
index 73a31d88..18d6a260 100644
--- a/test/concerns/orphan_strategies_test.rb
+++ b/test/concerns/orphan_strategies_test.rb
@@ -12,7 +12,7 @@ def test_setting_invalid_orphan_strategy
   end
 
   def test_orphan_rootify_strategy
-    AncestryTestDatabase.with_model orphan_strategy: :rootify, :depth => 3, :width => 3 do |model, roots|
+    AncestryTestDatabase.with_model orphan_strategy: :rootify, :depth => 3, :width => 3 do |_model, roots|
       root = roots.first.first
       children = root.children.to_a
       root.destroy
@@ -50,7 +50,7 @@ def verify_parent_exists
   end
 
   def test_orphan_restrict_strategy
-    AncestryTestDatabase.with_model orphan_strategy: :restrict, :depth => 3, :width => 3 do |model, roots|
+    AncestryTestDatabase.with_model orphan_strategy: :restrict, :depth => 3, :width => 3 do |_model, roots|
       root = roots.first.first
       assert_raise Ancestry::AncestryException do
         root.destroy
@@ -63,11 +63,11 @@ def test_orphan_restrict_strategy
 
   def test_orphan_adopt_strategy
     AncestryTestDatabase.with_model orphan_strategy: :adopt do |model|
-      n1 = model.create!                  #create a root node
-      n2 = model.create!(:parent => n1)   #create child with parent=root
-      n3 = model.create!(:parent => n2)   #create child with parent=n2, depth = 2
-      n4 = model.create!(:parent => n2)   #create child with parent=n2, depth = 2
-      n5 = model.create!(:parent => n4)   #create child with parent=n4, depth = 3
+      n1 = model.create!                  # create a root node
+      n2 = model.create!(:parent => n1)   # create child with parent=root
+      n3 = model.create!(:parent => n2)   # create child with parent=n2, depth = 2
+      n4 = model.create!(:parent => n2)   # create child with parent=n2, depth = 2
+      n5 = model.create!(:parent => n4)   # create child with parent=n4, depth = 3
       n2.destroy                          # delete a node with desecendants
       n3.reload
       n5.reload
@@ -84,7 +84,7 @@ def test_orphan_adopt_strategy
 
   # DEPRECATED - please see test_apply_orphan_strategy_none for pattern instead
   def test_override_apply_orphan_strategy
-    AncestryTestDatabase.with_model orphan_strategy: :destroy do |model, roots|
+    AncestryTestDatabase.with_model orphan_strategy: :destroy do |model, _roots|
       root  = model.create!
       child = model.create!(:parent => root)
       model.class_eval do
@@ -101,7 +101,7 @@ def apply_orphan_strategy
   end
 
   def test_apply_orphan_strategy_none
-    AncestryTestDatabase.with_model orphan_strategy: :none do |model, roots|
+    AncestryTestDatabase.with_model orphan_strategy: :none do |model, _roots|
       root  = model.create!
       child = model.create!(:parent => root)
       model.class_eval do
@@ -127,7 +127,7 @@ def apply_orphan_strategy_abc
         end
       end
 
-      root  = model.create!
+      root = model.create!
       3.times { root.children.create! }
       model.create! # a node that is not affected
       assert_difference 'model.count', -4 do
@@ -147,7 +147,7 @@ def apply_orphan_strategy_abc
 
         has_ancestry orphan_strategy: :abc, ancestry_column: AncestryTestDatabase.ancestry_column
       end
-      root  = model.create!
+      root = model.create!
       3.times { root.children.create! }
       model.create! # a node that is not affected
       assert_difference 'model.count', -4 do
@@ -158,17 +158,17 @@ def apply_orphan_strategy_abc
 
   def test_basic_delete
     AncestryTestDatabase.with_model do |model|
-      n1 = model.create!                  #create a root node
-      n2 = model.create!(:parent => n1)   #create child with parent=root
+      n1 = model.create!                      # create a root node
+      n2 = model.create!(:parent => n1)       # create child with parent=root
       n2.destroy!
-      model.find(n1.id)                   # parent should exist
+      model.find(n1.id)                       # parent should exist
 
-      n1 = model.create!                  #create a root node
-      n2 = model.create!(:parent => n1)   #create child with parent=root
+      n1 = model.create!                      # create a root node
+      n2 = model.create!(:parent => n1)       # create child with parent=root
       n1.destroy!
       assert_nil(model.find_by(:id => n2.id)) # child should not exist
 
-      n1 = model.create!                  #create a root node
+      n1 = model.create!                      # create a root node
       n1.destroy!
     end
   end
diff --git a/test/concerns/scopes_test.rb b/test/concerns/scopes_test.rb
index a765bafa..b31b168e 100644
--- a/test/concerns/scopes_test.rb
+++ b/test/concerns/scopes_test.rb
@@ -66,7 +66,7 @@ def test_order_by_reverse
     AncestryTestDatabase.with_model(:width => 1, :depth => 3) do |model, _roots|
       child = model.last
       assert child
-      assert_nothing_raised do #IrreversibleOrderError
+      assert_nothing_raised do # IrreversibleOrderError
         assert child.ancestors.last
       end
     end
@@ -106,9 +106,9 @@ def test_scoping_in_callbacks
       model.class_eval do
         define_method :after_create_callback do
           # We don't want to be in the #children scope here when creating the child
-          self.parent
+          parent
           self.parent_id = record.id if record
-          self.root
+          root
         end
       end
 
diff --git a/test/concerns/sort_by_ancestry_test.rb b/test/concerns/sort_by_ancestry_test.rb
index 6124cc35..03a34448 100644
--- a/test/concerns/sort_by_ancestry_test.rb
+++ b/test/concerns/sort_by_ancestry_test.rb
@@ -7,7 +7,7 @@ class SortByAncestryTest < ActiveSupport::TestCase
   # This highlights where/why a non-correct sorting order is returned
   CORRECT = (ENV["CORRECT"] == "true")
 
-  RANK_SORT = -> (a, b) { a.rank <=> b.rank }
+  RANK_SORT = ->(a, b) { a.rank <=> b.rank }
 
   # tree is of the form:
   #   - n1
@@ -19,7 +19,7 @@ class SortByAncestryTest < ActiveSupport::TestCase
   # @returns [Array<model>] list of nodes
   def build_tree(model)
     # inflate the node id to test id wrap around edge cases
-    ENV["NODES"].to_i.times { model.create!.destroy } if ENV["NODES"]
+    ENV["NODES"]&.to_i&.times { model.create!.destroy }
 
     n1 = model.create!
     n2 = model.create!(:parent => n1)
@@ -59,7 +59,7 @@ def test_sort_by_ancestry_no_parents_siblings
   end
 
   # TODO: thinking about dropping this one
-  # only keep if we can find a 
+  # only keep if we can find a way to sort in the db
   def test_sort_by_ancestry_no_parents_same_level
     AncestryTestDatabase.with_model do |model|
       _, _, n3, n4, n5, _ = build_tree(model)
@@ -118,7 +118,7 @@ def test_sort_by_ancestry_missing_parent_middle_of_tree
   def build_ranked_tree(model)
     # inflate the node id to test id wrap around edge cases
     # NODES=4..9 seem like edge cases
-    ENV["NODES"].to_i.times { model.create!.destroy } if ENV["NODES"]
+    ENV["NODES"]&.to_i&.times { model.create!.destroy }
 
     n1 = model.create!(:rank => 0)
     n2 = model.create!(:rank => 1)
diff --git a/test/concerns/sti_support_test.rb b/test/concerns/sti_support_test.rb
index 3b297820..123f481f 100644
--- a/test/concerns/sti_support_test.rb
+++ b/test/concerns/sti_support_test.rb
@@ -67,7 +67,7 @@ def test_sti_support_with_from_subclass
 
   def test_sti_support_for_counter_cache
     AncestryTestDatabase.with_model :counter_cache => true, :extra_columns => {:type => :string} do |model|
-      # NOTE had to use subclasses other than Subclass1/Subclass2 from above
+      # NOTE: had to use subclasses other than Subclass1/Subclass2 from above
       # due to (I think) Rails caching those STI classes and that not getting
       # reset between specs
 
diff --git a/test/concerns/touching_test.rb b/test/concerns/touching_test.rb
index 4f2d121a..2b912416 100644
--- a/test/concerns/touching_test.rb
+++ b/test/concerns/touching_test.rb
@@ -8,7 +8,6 @@ def test_touch_option_disabled
       :extra_columns => {:name => :string, :updated_at => :datetime},
       :touch => false
     ) do |model|
-
       wayback = Time.new(1984)
       recently = Time.now - 1.minute
 
@@ -27,7 +26,6 @@ def test_touch_option_enabled_propagates_with_modification
       :extra_columns => {:updated_at => :datetime},
       :touch => true
     ) do |model|
-
       way_back = Time.new(1984)
       recently = Time.now - 1.minute
 
@@ -54,7 +52,6 @@ def test_touch_option_enabled_propagates_with_modification
 
   def test_touch_propogates_multiple_levels
     AncestryTestDatabase.with_model(:extra_columns => {:name => :string, :updated_at => :datetime}, :touch => true) do |model|
-
       way_back = Time.new(1984)
       recently = Time.now - 1.minute
 
@@ -84,7 +81,6 @@ def test_touch_option_enabled_doesnt_propagate_without_modification
       :extra_columns => {:updated_at => :datetime},
       :touch => true
     ) do |model|
-
       way_back = Time.new(1984)
       recently = Time.now - 1.minute
 
@@ -107,7 +103,6 @@ def test_touch_option_with_scope
       :extra_columns => {:updated_at => :datetime},
       :touch => true
     ) do |model|
-
       way_back = Time.new(1984)
       recently = Time.now - 1.minute
 
diff --git a/test/concerns/tree_navigation_test.rb b/test/concerns/tree_navigation_test.rb
index a4e6fbb3..be61967d 100644
--- a/test/concerns/tree_navigation_test.rb
+++ b/test/concerns/tree_navigation_test.rb
@@ -9,15 +9,15 @@ class TreeNavigationTest < ActiveSupport::TestCase
   # across: |siblings|subtree    |path     |
   ATTRIBUTE_MATRIX = {
     root:        {attribute_id:  :root_id},
-    parent:      {attribute_id:  :parent_id,     exists: :has_parent?, db: true},
-    ancestors:   {attribute_ids: :ancestor_ids,  exists: :ancestors?,  db: true},
-    children:    {attribute_ids: :child_ids,     exists: :children?},
+    parent:      {attribute_id:  :parent_id,    exists: :has_parent?, db: true},
+    ancestors:   {attribute_ids: :ancestor_ids, exists: :ancestors?,  db: true},
+    children:    {attribute_ids: :child_ids,    exists: :children?},
     descendants: {attribute_ids: :descendant_ids},
     indirects:   {attribute_ids: :indirect_ids},
-    siblings:    {attribute_ids: :sibling_ids,   exists: :siblings?},
+    siblings:    {attribute_ids: :sibling_ids,  exists: :siblings?},
     subtree:     {attribute_ids: :subtree_ids},
-    path:        {attribute_ids: :path_ids, db: true},
-  }
+    path:        {attribute_ids: :path_ids, db: true}
+  }.freeze
   # NOTE: has_ancestors? is an alias for parent? / ancestors? but not tested
 
   # class level getters are in test/concerns/scopes_test.rb
@@ -196,7 +196,8 @@ def test_node_in_database_children
 
       # in database (again - but in a different hierarchy)
       node11.save!
-      node1.reload ; node2.reload
+      node1.reload
+      node2.reload
       # are these necessary?
       # do we want this to work without?
 
@@ -244,6 +245,7 @@ def update_descendants_with_new_ancestry
             raise "callback disabled for #{id}" if id == 2
           else
             raise "callback eabled for #{id}" if id != 2
+
             # want to make sure we're pointing at the correct nodes
             actual = unscoped_descendants_before_last_save.order(:id).map(&:id)
             raise "unscoped_descendants_before_last_save was #{actual}" unless actual == [3, 4, 5]
@@ -316,7 +318,7 @@ def assert_attribute(node, attribute_name, value, db: :value, exists: :value)
   # @param value [Array] expected output
   # @param attribute_name [Symbol] attribute to test
   # @param exists [true|false] test the exists "attribute? (default values.present?)
-  # @param db [Array[AR]]  value that should be reflected _in_database (default: use values) 
+  # @param db [Array[AR]]  value that should be reflected _in_database (default: use values)
   #                        skips if not supported in matrix
   def assert_attributes(node, attribute_name, values, db: :values, exists: :values)
     attribute_ids = ATTRIBUTE_MATRIX[attribute_name][:attribute_ids]
diff --git a/test/concerns/tree_predicate_test.rb b/test/concerns/tree_predicate_test.rb
index d2502646..38be4841 100644
--- a/test/concerns/tree_predicate_test.rb
+++ b/test/concerns/tree_predicate_test.rb
@@ -21,7 +21,7 @@ def test_tree_predicates
         # Children assertions
         assert root.has_children?
         assert !root.is_childless?
-        assert children.map { |n| n.is_childless? }.all?
+        assert children.map(&:is_childless?).all?
         assert children.map { |n| !root.child_of?(n) }.all?
         assert children.map { |n| n.child_of?(root) }.all?
         # Siblings assertions
diff --git a/test/environment.rb b/test/environment.rb
index 4176c4dc..0fa03d6f 100644
--- a/test/environment.rb
+++ b/test/environment.rb
@@ -62,7 +62,7 @@ def self.setup
 
       puts "testing #{db_type} #{Ancestry.default_update_strategy == :sql ? "(sql) " : ""}(with #{column_type} #{ancestry_column})"
       puts "column format: #{Ancestry.default_ancestry_format} options: #{column_options.inspect}"
-    rescue => e
+    rescue StandardError => e
       if ENV["CI"]
         raise
       else