Add validation to rule models

Ensure MR rule approvals_required > PR rule's

ee/app/models/approval_merge_request_rule.rb

@@ -15,6 +15,8 @@ class ApprovalMergeRequestRule < ApplicationRecord
   has_one :approval_merge_request_rule_source
   has_one :approval_project_rule, through: :approval_merge_request_rule_source
 
+  validate :validate_approvals_required
+
   def project
     merge_request.target_project
   end
@@ -44,4 +46,15 @@ class ApprovalMergeRequestRule < ApplicationRecord
     !code_owner?
   end
   alias_method :regular?, :regular
+
+  private
+
+  def validate_approvals_required
+    return unless approval_project_rule
+    return unless approvals_required_changed?
+
+    if approvals_required < approval_project_rule.approvals_required
+      errors.add(:approvals_required, :greater_than_or_equal_to, count: approval_project_rule.approvals_required)
+    end
+  end
 end

ee/app/models/concerns/approval_rule_like.rb

@@ -12,7 +12,7 @@ module ApprovalRuleLike
     has_many :group_users, -> { distinct }, through: :groups, source: :users
 
     validates :name, presence: true
-    validates :approvals_required, numericality: { less_than_or_equal_to: APPROVALS_REQUIRED_MAX }
+    validates :approvals_required, numericality: { less_than_or_equal_to: APPROVALS_REQUIRED_MAX, greater_than_or_equal_to: 0 }
   end
 
   # Users who are eligible to approve, including specified group members.

ee/spec/models/approval_merge_request_rule_spec.rb

@@ -85,4 +85,32 @@ describe ApprovalMergeRequestRule do
       end
     end
   end
+
+  describe 'validations' do
+    describe 'approvals_required' do
+      subject { build(:approval_merge_request_rule, merge_request: merge_request) }
+
+      it 'is a natual number' do
+        subject.assign_attributes(approvals_required: 2)
+        expect(subject).to be_valid
+
+        subject.assign_attributes(approvals_required: 0)
+        expect(subject).to be_valid
+
+        subject.assign_attributes(approvals_required: -1)
+        expect(subject).to be_invalid
+      end
+
+      context 'when project rule is present' do
+        let(:project_rule) { create(:approval_project_rule, project: merge_request.project, approvals_required: 3) }
+
+        it 'has to be greater than or equal to project rule approvals_required' do
+          subject.assign_attributes(approval_project_rule: project_rule, approvals_required: 2)
+          subject.valid?
+
+          expect(subject.errors[:approvals_required]).to include("must be greater than or equal to 3")
+        end
+      end
+    end
+  end
 end