Validate multiple polices only on create

ee/app/models/incident_management/escalation_policy.rb

@@ -7,7 +7,7 @@ module IncidentManagement
     belongs_to :project
     has_many :rules, class_name: 'EscalationRule', inverse_of: :policy, foreign_key: 'policy_id', index_errors: true
 
-    validates :project_id, uniqueness: { message: _('can only have one escalation policy') }
+    validates :project_id, uniqueness: { message: _('can only have one escalation policy') }, on: :create
     validates :name, presence: true, uniqueness: { scope: [:project_id] }, length: { maximum: 72 }
     validates :description, length: { maximum: 160 }
     validates :rules, presence: true

ee/spec/models/incident_management/escalation_policy_spec.rb

@@ -17,7 +17,7 @@ RSpec.describe IncidentManagement::EscalationPolicy do
   describe 'validations' do
     it { is_expected.to validate_presence_of(:name) }
     it { is_expected.to validate_presence_of(:rules) }
-    it { is_expected.to validate_uniqueness_of(:project_id).with_message(/can only have one escalation policy/) }
+    it { is_expected.to validate_uniqueness_of(:project_id).with_message(/can only have one escalation policy/).on(:create) }
     it { is_expected.to validate_uniqueness_of(:name).scoped_to(:project_id) }
     it { is_expected.to validate_length_of(:name).is_at_most(72) }
     it { is_expected.to validate_length_of(:description).is_at_most(160) }