1 files changed, 111 insertions, 0 deletions
diff --git a/spec/rubocop/cop/performance/ar_exists_and_present_blank_spec.rb b/spec/rubocop/cop/performance/ar_exists_and_present_blank_spec.rb
new file mode 100644
index 00000000000..ce4fdac56b0
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+++ b/spec/rubocop/cop/performance/ar_exists_and_present_blank_spec.rb
@@ -0,0 +1,111 @@
+# frozen_string_literal: true
+
+require 'fast_spec_helper'
+require_relative '../../../support/helpers/expect_offense'
+require_relative '../../../../rubocop/cop/performance/ar_exists_and_present_blank.rb'
+
+describe RuboCop::Cop::Performance::ARExistsAndPresentBlank do
+  include CopHelper
+  include ExpectOffense
+
+  subject(:cop) { described_class.new }
+
+  context 'when it is not haml file' do
+    it 'does not flag it as an offense' do
+      expect(subject).to receive(:in_haml_file?).with(anything).at_least(:once).and_return(false)
+
+      expect_no_offenses <<~SOURCE
+        return unless @users.exists?
+        show @users if @users.present?
+      SOURCE
+    end
+  end
+
+  context 'when it is haml file' do
+    before do
+      expect(subject).to receive(:in_haml_file?).with(anything).at_least(:once).and_return(true)
+    end
+
+    context 'the same object uses exists? and present?' do
+      it 'flags it as an offense' do
+        expect_offense <<~SOURCE
+        return unless @users.exists?
+        show @users if @users.present?
+                       ^^^^^^^^^^^^^^^ Avoid `@users.present?`, because it will generate database query 'Select TABLE.*' which is expensive. Suggest to use `@users.any?` to replace `@users.present?`
+        SOURCE
+
+        expect(cop.offenses.map(&:cop_name)).to contain_exactly('Performance/ARExistsAndPresentBlank')
+      end
+    end
+
+    context 'the same object uses exists? and blank?' do
+      it 'flags it as an offense' do
+        expect_offense <<~SOURCE
+        return unless @users.exists?
+        show @users if @users.blank?
+                       ^^^^^^^^^^^^^ Avoid `@users.blank?`, because it will generate database query 'Select TABLE.*' which is expensive. Suggest to use `@users.empty?` to replace `@users.blank?`
+        SOURCE
+
+        expect(cop.offenses.map(&:cop_name)).to contain_exactly('Performance/ARExistsAndPresentBlank')
+      end
+    end
+
+    context 'the same object uses exists?, blank? and present?' do
+      it 'flags it as an offense' do
+        expect_offense <<~SOURCE
+        return unless @users.exists?
+        show @users if @users.blank?
+                       ^^^^^^^^^^^^^ Avoid `@users.blank?`, because it will generate database query 'Select TABLE.*' which is expensive. Suggest to use `@users.empty?` to replace `@users.blank?`
+        show @users if @users.present?
+                       ^^^^^^^^^^^^^^^ Avoid `@users.present?`, because it will generate database query 'Select TABLE.*' which is expensive. Suggest to use `@users.any?` to replace `@users.present?`
+        SOURCE
+
+        expect(cop.offenses.map(&:cop_name)).to contain_exactly('Performance/ARExistsAndPresentBlank', 'Performance/ARExistsAndPresentBlank')
+      end
+    end
+
+    RSpec.shared_examples 'different object uses exists? and present?/blank?' do |another_method|
+      it 'does not flag it as an offense' do
+        expect_no_offenses <<~SOURCE
+        return unless @users.exists?
+        present @emails if @emails.#{another_method}
+        SOURCE
+      end
+    end
+
+    it_behaves_like 'different object uses exists? and present?/blank?', 'present?'
+    it_behaves_like 'different object uses exists? and present?/blank?', 'blank?'
+
+    RSpec.shared_examples 'Only using one present?/blank? without exists?' do |non_exists_method|
+      it 'does not flag it as an offense' do
+        expect_no_offenses "@users.#{non_exists_method}"
+      end
+    end
+
+    it_behaves_like 'Only using one present?/blank? without exists?', 'present?'
+    it_behaves_like 'Only using one present?/blank? without exists?', 'blank?'
+
+    context 'when using many present?/empty? without exists?' do
+      it 'does not flag it as an offense' do
+        expect_no_offenses <<~SOURCE
+        @user.present?
+        @user.blank?
+        @user.present?
+        @user.blank?
+        SOURCE
+      end
+    end
+
+    context 'when just using exists? without present?/blank?' do
+      it 'does not flag it as an offense' do
+        expect_no_offenses '@users.exists?'
+
+        expect_no_offenses <<~SOURCE
+        @users.exists?
+        @users.some_other_method?
+        @users.exists?
+        SOURCE
+      end
+    end
+  end
+end