Implement LegacyStagePresenter specs

spec/presenters/ci/legacy_stage_presenter_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe Ci::LegacyStagePresenter do
+  let(:legacy_stage) { create(:ci_stage) }
+
+  describe '#preloaded_statuses' do
+    subject(:preloaded_statuses) { described_class.new(legacy_stage).preloaded_statuses }
+
+    let!(:build) { create(:ci_build, :tags, pipeline: legacy_stage.pipeline, stage: legacy_stage.name) }
+
+    before do
+      create(:generic_commit_status, pipeline: legacy_stage.pipeline, stage: legacy_stage.name)
+    end
+
+    it 'preloads build tags' do
+      expect(preloaded_statuses.first.association(:tags)).to be_loaded
+    end
+  end
+end