Destroy related lists when a label is removed

app/models/label.rb

@@ -13,6 +13,8 @@ class Label < ActiveRecord::Base
   default_value_for :color, DEFAULT_COLOR
 
   belongs_to :project
+
+  has_many :lists, dependent: :destroy
   has_many :label_links, dependent: :destroy
   has_many :issues, through: :label_links, source: :target, source_type: 'Issue'
   has_many :merge_requests, through: :label_links, source: :target, source_type: 'MergeRequest'

spec/models/label_spec.rb

@@ -5,8 +5,10 @@ describe Label, models: true do
 
   describe 'associations' do
     it { is_expected.to belong_to(:project) }
+
     it { is_expected.to have_many(:label_links).dependent(:destroy) }
     it { is_expected.to have_many(:issues).through(:label_links).source(:target) }
+    it { is_expected.to have_many(:lists).dependent(:destroy) }
   end
 
   describe 'modules' do