diff --git a/.rubocop.yml b/.rubocop.yml
index 15bd835..b5a58ca 100644
--- a/.rubocop.yml
+++ b/.rubocop.yml
@@ -17,3 +17,5 @@ Layout/EndAlignment:
   EnforcedStyleAlignWith: variable
 Layout/FirstArrayElementIndentation:
   EnforcedStyle: consistent
+Gemspec/DevelopmentDependencies:
+  Enabled: false
diff --git a/lib/nazar.rb b/lib/nazar.rb
index 2543ca6..a125fd9 100644
--- a/lib/nazar.rb
+++ b/lib/nazar.rb
@@ -33,7 +33,7 @@ module Nazar # rubocop:disable Metrics/ModuleLength
 
   setting :enable_shorthand_method, default: true
 
-  class << self
+  class << self # rubocop:disable Metrics/ClassLength
     def formatters
       @formatters ||= Set.new
     end
diff --git a/lib/nazar/formatter/generic.rb b/lib/nazar/formatter/generic.rb
index 451574f..cbd3b91 100644
--- a/lib/nazar/formatter/generic.rb
+++ b/lib/nazar/formatter/generic.rb
@@ -27,7 +27,7 @@ def summary
       end
 
       def self.valid?(data)
-        return unless data.is_a?(Enumerable)
+        return false unless data.is_a?(Enumerable)
 
         item = data&.first
         item.respond_to?(:keys) && item.respond_to?(:values)
diff --git a/lib/nazar/formatter/struct.rb b/lib/nazar/formatter/struct.rb
index d5f0502..5be1eb9 100644
--- a/lib/nazar/formatter/struct.rb
+++ b/lib/nazar/formatter/struct.rb
@@ -3,7 +3,6 @@
 module Nazar
   module Formatter
     class Struct
-
       def initialize(item)
         @collection = Array(item)
         @attributes = item.to_h.keys
@@ -24,7 +23,7 @@ def headers
 
       def cells
         @cells ||= @collection.map do |item|
-          item.each_pair do |column, value|
+          item.each_pair do |_, value|
             CellFormatter.new(value, type: nil).format
           end
         end
diff --git a/spec/nazar/view_spec.rb b/spec/nazar/view_spec.rb
index 0973a0c..b563916 100644
--- a/spec/nazar/view_spec.rb
+++ b/spec/nazar/view_spec.rb
@@ -66,7 +66,6 @@
     context 'with Struct' do
       let(:data) { Struct.new(:id, :name).new(1, 'foo') }
 
-
       context 'without loaded extension' do
         it do
           expect(subject).not_to be_supported_data
diff --git a/spec/nazar_spec.rb b/spec/nazar_spec.rb
index f55e8c9..f48cc71 100644
--- a/spec/nazar_spec.rb
+++ b/spec/nazar_spec.rb
@@ -15,7 +15,7 @@
 
     context 'when Pry is defined' do
       it do
-        ::Pry = double
+        ::Pry = double # rubocop:disable Style/RedundantConstantBase
 
         expect(Nazar).to receive(:enable_for_pry!)
         expect(Nazar).not_to receive(:enable_for_irb!)
@@ -26,7 +26,7 @@
 
     context 'when IRB is defined' do
       it do
-        ::IRB = double
+        ::IRB = double # rubocop:disable Style/RedundantConstantBase
 
         expect(Nazar).not_to receive(:enable_for_pry!)
         expect(Nazar).to receive(:enable_for_irb!)