Add overrides test

spec/lib/overrides_spec.rb

@@ -0,0 +1,36 @@
+# frozen_string_literal: true
+
+require "spec_helper"
+
+# We check the checksum of the file overriden.
+# If the test fails, that the overriden file should be updated.
+checksums = [
+  {
+    package: "decidim-core",
+    files: {
+      "/app/cells/decidim/newsletter_templates/basic_only_text/show.erb" => "6f85f6b733a6db3b11f9cabb19ae4126",
+      "/app/cells/decidim/newsletter_templates/basic_only_text_settings_form/show.erb" => "8266085960926e21d0a7e7572eb83c7b",
+      "/app/cells/decidim/newsletter_templates/image_text_cta/show.erb" => "606f899f03d5e4e6d3c1691132eeb2ac",
+      "/app/cells/decidim/newsletter_templates/image_text_cta_settings_form/show.erb" => "2d3acf3d142dd85d150583bce65fbb1c",
+    }
+  }
+]
+
+describe "Overriden files", type: :view do
+  checksums.each do |item|
+    # rubocop:disable Rails/DynamicFindBy
+    spec = ::Gem::Specification.find_by_name(item[:package])
+    # rubocop:enable Rails/DynamicFindBy
+    item[:files].each do |file, signature|
+      it "#{spec.gem_dir}#{file} matches checksum" do
+        expect(md5("#{spec.gem_dir}#{file}")).to eq(signature)
+      end
+    end
+  end
+
+  private
+
+  def md5(file)
+    Digest::MD5.hexdigest(File.read(file))
+  end
+end