Introduce ReportsComparer class

This commits extracts the business logic required to build a diff
report between the head and the base pipeline. This logic has been
extracted to an abstract class to facilitate future report comparison.

lib/gitlab/ci/reports/accessibility_reports_comparer.rb

@@ -3,21 +3,14 @@
 module Gitlab
   module Ci
     module Reports
-      class AccessibilityReportsComparer
-        include Gitlab::Utils::StrongMemoize
-
-        STATUS_SUCCESS = 'success'
-        STATUS_FAILED = 'failed'
-
-        attr_reader :base_report, :head_report
-
+      class AccessibilityReportsComparer < ReportsComparer
         def initialize(base_report, head_report)
           @base_report = base_report || AccessibilityReports.new
           @head_report = head_report
         end
 
-        def status
-          head_report.errors_count > 0 ? STATUS_FAILED : STATUS_SUCCESS
+        def success?
+          head_report.errors_count == 0
         end
 
         def existing_errors

lib/gitlab/ci/reports/codequality_reports_comparer.rb

@@ -3,21 +3,14 @@
 module Gitlab
   module Ci
     module Reports
-      class CodequalityReportsComparer
-        include Gitlab::Utils::StrongMemoize
-
-        STATUS_SUCCESS = 'success'
-        STATUS_FAILED = 'failed'
-
-        attr_reader :base_report, :head_report
-
+      class CodequalityReportsComparer < ReportsComparer
         def initialize(base_report, head_report)
           @base_report = base_report || CodequalityReports.new
           @head_report = head_report
         end
 
-        def status
-          head_report.degradations_count > 0 ? STATUS_FAILED : STATUS_SUCCESS
+        def success?
+          head_report.degradations_count == 0
         end
 
         def existing_errors
@@ -40,17 +33,15 @@ module Gitlab
           end
         end
 
-        def errors_count
-          head_report.degradations_count
-        end
-
         def resolved_count
           resolved_errors.size
         end
 
         def total_count
-          existing_errors.size + new_errors.size
+          head_report.degradations_count
         end
+
+        alias_method :errors_count, :total_count
       end
     end
   end

lib/gitlab/ci/reports/reports_comparer.rb

+# frozen_string_literal: true
+
+module Gitlab
+  module Ci
+    module Reports
+      class ReportsComparer
+        include Gitlab::Utils::StrongMemoize
+
+        STATUS_SUCCESS = 'success'
+        STATUS_FAILED = 'failed'
+
+        attr_reader :base_report, :head_report
+
+        def initialize(base_report, head_report)
+          @base_report = base_report
+          @head_report = head_report
+        end
+
+        def status
+          success? ? STATUS_SUCCESS : STATUS_FAILED
+        end
+
+        def success?
+          raise NotImplementedError
+        end
+
+        def existing_errors
+          raise NotImplementedError
+        end
+
+        def new_errors
+          raise NotImplementedError
+        end
+
+        def resolved_errors
+          raise NotImplementedError
+        end
+
+        def errors_count
+          raise NotImplementedError
+        end
+
+        def resolved_count
+          resolved_errors.size
+        end
+
+        def total_count
+          existing_errors.size + new_errors.size
+        end
+      end
+    end
+  end
+end

spec/lib/gitlab/ci/reports/reports_comparer_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe Gitlab::Ci::Reports::ReportsComparer do
+  let(:comparer) { described_class.new(base_report, head_report) }
+  let(:base_report) { Gitlab::Ci::Reports::CodequalityReports.new }
+  let(:head_report) { Gitlab::Ci::Reports::CodequalityReports.new }
+
+  describe '#initialize' do
+    context 'sets getter for the report comparer' do
+      it 'return base report' do
+        expect(comparer.base_report).to be_an_instance_of(Gitlab::Ci::Reports::CodequalityReports)
+      end
+
+      it 'return head report' do
+        expect(comparer.head_report).to be_an_instance_of(Gitlab::Ci::Reports::CodequalityReports)
+      end
+    end
+  end
+
+  describe '#status' do
+    subject(:status) { comparer.status }
+
+    it 'returns not implemented error' do
+      expect { status }.to raise_error(NotImplementedError)
+    end
+
+    context 'when success? is true' do
+      before do
+        allow(comparer).to receive(:success?).and_return(true)
+      end
+
+      it 'returns status success' do
+        expect(status).to eq('success')
+      end
+    end
+
+    context 'when success? is false' do
+      before do
+        allow(comparer).to receive(:success?).and_return(false)
+      end
+
+      it 'returns status failed' do
+        expect(status).to eq('failed')
+      end
+    end
+  end
+
+  describe '#success?' do
+    subject(:success?) { comparer.success? }
+
+    it 'returns not implemented error' do
+      expect { success? }.to raise_error(NotImplementedError)
+    end
+  end
+
+  describe '#existing_errors' do
+    subject(:existing_errors) { comparer.existing_errors }
+
+    it 'returns not implemented error' do
+      expect { existing_errors }.to raise_error(NotImplementedError)
+    end
+  end
+
+  describe '#resolved_errors' do
+    subject(:resolved_errors) { comparer.resolved_errors }
+
+    it 'returns not implemented error' do
+      expect { resolved_errors }.to raise_error(NotImplementedError)
+    end
+  end
+
+  describe '#errors_count' do
+    subject(:errors_count) { comparer.errors_count }
+
+    it 'returns not implemented error' do
+      expect { errors_count }.to raise_error(NotImplementedError)
+    end
+  end
+
+  describe '#resolved_count' do
+    subject(:resolved_count) { comparer.resolved_count }
+
+    it 'returns not implemented error' do
+      expect { resolved_count }.to raise_error(NotImplementedError)
+    end
+  end
+
+  describe '#total_count' do
+    subject(:total_count) { comparer.total_count }
+
+    it 'returns not implemented error' do
+      expect { total_count }.to raise_error(NotImplementedError)
+    end
+  end
+end