1 files changed, 29 insertions, 0 deletions
diff --git a/spec/migrations/add_epics_relative_position_spec.rb b/spec/migrations/add_epics_relative_position_spec.rb
new file mode 100644
index 00000000000..f3b7dd1727b
--- /dev/null
+++ b/spec/migrations/add_epics_relative_position_spec.rb
@@ -0,0 +1,29 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+require_migration!
+
+RSpec.describe AddEpicsRelativePosition, :migration do
+  let(:groups) { table(:namespaces) }
+  let(:epics) { table(:epics) }
+  let(:users) { table(:users) }
+  let(:user) { users.create!(name: 'user', email: 'email@example.org', projects_limit: 100) }
+  let(:group) { groups.create!(name: 'gitlab', path: 'gitlab-org', type: 'Group') }
+
+  let!(:epic1) { epics.create!(title: 'epic 1', title_html: 'epic 1', author_id: user.id, group_id: group.id, iid: 1) }
+  let!(:epic2) { epics.create!(title: 'epic 2', title_html: 'epic 2', author_id: user.id, group_id: group.id, iid: 2) }
+  let!(:epic3) { epics.create!(title: 'epic 3', title_html: 'epic 3', author_id: user.id, group_id: group.id, iid: 3) }
+
+  it 'does nothing if epics table contains relative_position' do
+    expect { migrate! }.not_to change { epics.pluck(:relative_position) }
+  end
+
+  it 'adds relative_position if missing and backfills it with ID value', :aggregate_failures do
+    ActiveRecord::Base.connection.execute('ALTER TABLE epics DROP relative_position')
+
+    migrate!
+
+    expect(epics.pluck(:relative_position)).to match_array([epic1.id * 500, epic2.id * 500, epic3.id * 500])
+  end
+end