add initializer to test_app task

Rakefile

@@ -1,6 +1,7 @@
 # frozen_string_literal: true
 
 require "decidim/dev/common_rake"
+require "fileutils"
 
 def install_module(path)
   Dir.chdir(path) do
@@ -9,6 +10,15 @@ def install_module(path)
   end
 end
 
+def install_initializer(path, _env)
+  Dir.chdir(path) do
+    FileUtils.cp(
+      "#{__dir__}/lib/generators/decidim/app_templates/#env}/initializer.rb",
+      "config/initializers/decidim_term_customizer_config.rb"
+    )
+  end
+end
+
 def seed_db(path)
   Dir.chdir(path) do
     system("bundle exec rake db:seed")
@@ -18,6 +28,7 @@ end
 desc "Generates a dummy app for testing"
 task test_app: "decidim:generate_external_test_app" do
   ENV["RAILS_ENV"] = "test"
+  install_initializer("spec/decidim_dummy_app", "test")
   install_module("spec/decidim_dummy_app")
 end