Add SystemNodes::IncidentService class

Allows to add system notes on change severity status for incidents

app/helpers/system_note_helper.rb

@@ -34,7 +34,8 @@ module SystemNoteHelper
     'designs_discussion_added' => 'doc-image',
     'status' => 'status',
     'alert_issue_added' => 'issues',
-    'new_alert_added' => 'warning'
+    'new_alert_added' => 'warning',
+    'severity' => 'information-o'
   }.freeze
 
   def system_note_icon_name(note)

app/models/issuable_severity.rb

@@ -2,6 +2,13 @@
 
 class IssuableSeverity < ApplicationRecord
   DEFAULT = 'unknown'
+  SEVERITY_LABELS = {
+    unknown:  'Unknown',
+    low:      'Low - S4',
+    medium:   'Medium - S3',
+    high:     'High - S2',
+    critical: 'Critical - S1'
+  }.freeze
 
   belongs_to :issue
 

app/models/system_note_metadata.rb

@@ -20,7 +20,7 @@ class SystemNoteMetadata < ApplicationRecord
     title time_tracking branch milestone discussion task moved
     opened closed merged duplicate locked unlocked outdated
     tag due_date pinned_embed cherry_pick health_status approved unapproved
-    status alert_issue_added relate unrelate new_alert_added
+    status alert_issue_added relate unrelate new_alert_added severity
   ].freeze
 
   validates :note, presence: true

app/services/system_note_service.rb

@@ -308,6 +308,10 @@ module SystemNoteService
     ::SystemNotes::AlertManagementService.new(noteable: alert, project: alert.project).create_new_alert(monitoring_tool)
   end
 
+  def change_incident_severity(incident, author)
+    ::SystemNotes::IncidentService.new(noteable: incident, project: incident.project, author: author).change_incident_severity
+  end
+
   private
 
   def merge_requests_service(noteable, project, author)

app/services/system_notes/incident_service.rb

+# frozen_string_literal: true
+
+module SystemNotes
+  class IncidentService < ::SystemNotes::BaseService
+    # Called when the severity of an Incident has changed
+    #
+    # Example Note text:
+    #
+    #   "changed the severity to Medium - S3"
+    #
+    # Returns the created Note object
+    def change_incident_severity
+      severity = noteable.severity
+      severity_label = IssuableSeverity::SEVERITY_LABELS.fetch(severity.to_sym)
+      body = "changed the severity to **#{severity_label}**"
+
+      create_note(NoteSummary.new(noteable, project, author, body, action: 'severity'))
+    end
+  end
+end

spec/services/system_note_service_spec.rb

@@ -741,4 +741,16 @@ RSpec.describe SystemNoteService do
       described_class.create_new_alert(alert, monitoring_tool)
     end
   end
+
+  describe '.change_incident_severity' do
+    let(:incident) { build(:incident) }
+
+    it 'calls IncidentService' do
+      expect_next_instance_of(SystemNotes::IncidentService) do |service|
+        expect(service).to receive(:change_incident_severity)
+      end
+
+      described_class.change_incident_severity(incident, author)
+    end
+  end
 end

spec/services/system_notes/incident_service_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe ::SystemNotes::IncidentService do
+  let_it_be(:author) { create(:user) }
+  let_it_be(:project) { create(:project) }
+  let_it_be(:noteable) { create(:incident, project: project) }
+  let_it_be(:issuable_severity) { create(:issuable_severity, issue: noteable, severity: :medium) }
+
+  describe '#change_incident_severity' do
+    subject(:change_severity) { described_class.new(noteable: noteable, project: project, author: author).change_incident_severity }
+
+    it_behaves_like 'a system note' do
+      let(:action) { 'severity' }
+    end
+
+    IssuableSeverity.severities.keys.each do |severity|
+      context "with #{severity} severity" do
+        before do
+          issuable_severity.update!(severity: severity)
+        end
+
+        it 'has the appropriate message' do
+          severity_label = IssuableSeverity::SEVERITY_LABELS.fetch(severity.to_sym)
+
+          expect(change_severity.note).to eq("changed the severity to **#{severity_label}**")
+        end
+      end
+    end
+  end
+end