Add --spec option for data_update generator (#11245)

docs/backend/data-update-scripts.md

@@ -40,6 +40,26 @@ module DataUpdateScripts
 end
 ```
 
+The generator will also automatically create the corresponding spec file.
+
+```ruby
+require "rails_helper"
+require Rails.root.join(
+  "20201103042915_backfill_column_for_articles.rb",
+)
+
+describe DataUpdateScripts::BackfillColumnForArticles do
+  pending "add some examples to (or delete) #{__FILE__}"
+end
+```
+
+While we encourage adding tests for data update scripts, you can skip spec
+creation by adding the `--no-spec` option to the `rails generate` command:
+
+```
+rails generate data_update BackfillColumnForArticles --no-spec
+```
+
 Once your script is in place then you can either run `rails data_updates:run`
 manually or you can let our setup script handle it. In our local
 [bin/setup](https://github.com/forem/forem/blob/master/bin/setup) script you

lib/generators/data_update/data_update_generator.rb

@@ -1,11 +1,22 @@
 class DataUpdateGenerator < Rails::Generators::NamedBase
   source_root File.expand_path("templates", __dir__)
+  class_option :spec, type: :boolean, default: true
 
   def create_data_update_file
     template(
       "data_update.rb.tt",
-      File.join("lib", "data_update_scripts", class_path,
-                "#{Time.current.utc.strftime('%Y%m%d%H%M%S')}_#{file_name}.rb"),
+      File.join("lib", "data_update_scripts", class_path, script_name),
+    )
+
+    return unless options["spec"]
+
+    template(
+      "data_update_spec.rb.tt",
+      File.join("spec", "lib", "data_update_scripts", class_path, "#{file_name}_spec.rb"),
     )
   end
+
+  def script_name
+    @script_name ||= "#{Time.current.utc.strftime('%Y%m%d%H%M%S')}_#{file_name}.rb"
+  end
 end

lib/generators/data_update/templates/data_update_spec.rb.tt

@@ -0,0 +1,8 @@
+require "rails_helper"
+require Rails.root.join(
+  "<%= script_name %>",
+)
+
+describe DataUpdateScripts::<%= class_name %> do
+  pending "add some examples to (or delete) #{__FILE__}"
+end