add spec to verify that generating test locales works

spec/integration/generated_locale_spec.rb

@@ -0,0 +1,17 @@
+# frozen_string_literal: true
+
+require "rails_helper"
+
+describe "test locale generation" do
+  before(:context) { Rails.application.load_tasks }
+
+  it "succeeds" do
+    allow($stdout).to receive(:puts)
+
+    Rake::Task["locale:generate"].invoke
+
+    %w[activerecord controllers errors frontend views voc].each do |locale_type|
+      expect($stdout).to have_received(:puts).with a_string_including("generating #{locale_type}.en-xx.yml")
+    end
+  end
+end