diff --git a/.rubocop.yml b/.rubocop.yml
index 50263f3..25104f3 100644
--- a/.rubocop.yml
+++ b/.rubocop.yml
@@ -2,6 +2,10 @@ require:
   - rubocop-performance
   - rubocop-rspec
 
+AllCops:
+  NewCops: enable
+  SuggestExtensions: false
+
 Style/FrozenStringLiteralComment:
   Enabled: false
 
@@ -76,3 +80,20 @@ Naming/PredicateName:
 Naming/AccessorMethodName:
   Exclude:
     - 'lib/**/**.rb'
+
+Style/CaseLikeIf:
+  Exclude:
+    - 'lib/fast_jsonapi/object_serializer.rb'
+
+Style/OptionalBooleanParameter:
+  Exclude:
+    - 'lib/fast_jsonapi/serialization_core.rb'
+    - 'lib/fast_jsonapi/relationship.rb'
+
+Lint/DuplicateBranch:
+  Exclude:
+    - 'lib/fast_jsonapi/relationship.rb'
+
+Style/DocumentDynamicEvalDefinition:
+  Exclude:
+    - 'lib/extensions/has_one.rb'
diff --git a/lib/fast_jsonapi/object_serializer.rb b/lib/fast_jsonapi/object_serializer.rb
index 874b7be..26dd5f5 100644
--- a/lib/fast_jsonapi/object_serializer.rb
+++ b/lib/fast_jsonapi/object_serializer.rb
@@ -228,10 +228,10 @@ module FastJsonapi
 
         # TODO: Remove this undocumented option.
         #   Delegate the caching to the serializer exclusively.
-        if !relationship.cached
-          uncachable_relationships_to_serialize[relationship.name] = relationship
-        else
+        if relationship.cached
           cachable_relationships_to_serialize[relationship.name] = relationship
+        else
+          uncachable_relationships_to_serialize[relationship.name] = relationship
         end
         relationships_to_serialize[relationship.name] = relationship
       end
@@ -302,7 +302,7 @@ module FastJsonapi
 
       def serializer_for(name)
         namespace = self.name.gsub(/()?\w+Serializer$/, '')
-        serializer_name = name.to_s.demodulize.classify + 'Serializer'
+        serializer_name = "#{name.to_s.demodulize.classify}Serializer"
         serializer_class_name = namespace + serializer_name
         begin
           serializer_class_name.constantize
@@ -340,7 +340,7 @@ module FastJsonapi
       def validate_includes!(includes)
         return if includes.blank?
 
-        parse_includes_list(includes).keys.each do |include_item|
+        parse_includes_list(includes).each_key do |include_item|
           relationship_to_include = relationships_to_serialize[include_item]
           raise(JSONAPI::Serializer::UnsupportedIncludeError.new(include_item, name)) unless relationship_to_include
 
diff --git a/lib/fast_jsonapi/relationship.rb b/lib/fast_jsonapi/relationship.rb
index cc26d70..4a36932 100644
--- a/lib/fast_jsonapi/relationship.rb
+++ b/lib/fast_jsonapi/relationship.rb
@@ -12,7 +12,12 @@ module FastJsonapi
       object_block:,
       serializer:,
       relationship_type:,
-      polymorphic:, conditional_proc:, transform_method:, links:, meta:, cached: false,
+      polymorphic:,
+      conditional_proc:,
+      transform_method:,
+      links:,
+      meta:,
+      cached: false,
       lazy_load_data: false
     )
       @owner = owner
diff --git a/lib/jsonapi/serializer/errors.rb b/lib/jsonapi/serializer/errors.rb
index 7272eec..0faca6f 100644
--- a/lib/jsonapi/serializer/errors.rb
+++ b/lib/jsonapi/serializer/errors.rb
@@ -8,6 +8,7 @@ module JSONAPI
       attr_reader :include_item, :klass
 
       def initialize(include_item, klass)
+        super()
         @include_item = include_item
         @klass = klass
       end
diff --git a/spec/fixtures/movie.rb b/spec/fixtures/movie.rb
index a8a086d..f99af21 100644
--- a/spec/fixtures/movie.rb
+++ b/spec/fixtures/movie.rb
@@ -26,7 +26,7 @@ class Movie
     @url ||= FFaker::Internet.http_url
     return @url if obj.nil?
 
-    @url + '?' + obj.hash.to_s
+    "#{@url}?#{obj.hash}"
   end
 
   def owner=(ownr)
diff --git a/spec/integration/instrumentation_spec.rb b/spec/integration/instrumentation_spec.rb
index 59ad425..1a106ee 100644
--- a/spec/integration/instrumentation_spec.rb
+++ b/spec/integration/instrumentation_spec.rb
@@ -10,10 +10,8 @@ RSpec.describe JSONAPI::Serializer do
 
   it do
     payload = event_name = nil
-    notification_name = (
-      ::JSONAPI::Serializer::Instrumentation::NOTIFICATION_NAMESPACE +
-        'serializable_hash'
-    )
+    notification_name =
+      "#{::JSONAPI::Serializer::Instrumentation::NOTIFICATION_NAMESPACE}serializable_hash"
 
     ActiveSupport::Notifications.subscribe(
       notification_name