Rails 3.1: Engine vs. Mountable App

rename_column :table, :old_column, :new_column

You'll probably want to create a separate migration to do this. (Rename FixColumnName as you will.):

script/generate migration FixColumnName
# creates  db/migrate/xxxxxxxxxx_fix_column_name.rb

Then edit the migration to do your will:

# db/migrate/xxxxxxxxxx_fix_column_name.rb
class FixColumnName < ActiveRecord::Migration
  def self.up
    rename_column :table_name, :old_column, :new_column
  end

  def self.down
    # rename back if you need or do something else or do nothing
  end
end

For Rails 3.1 use:

While, the up and down methods still apply, Rails 3.1 receives a change method that "knows how to migrate your database and reverse it when the migration is rolled back without the need to write a separate down method".

See "Active Record Migrations" for more information.

rails g migration FixColumnName

class FixColumnName < ActiveRecord::Migration
  def change
    rename_column :table_name, :old_column, :new_column
  end
end

If you happen to have a whole bunch of columns to rename, or something that would have required repeating the table name over and over again:

rename_column :table_name, :old_column1, :new_column1
rename_column :table_name, :old_column2, :new_column2
...

You could use change_table to keep things a little neater:

class FixColumnNames < ActiveRecord::Migration
  def change
    change_table :table_name do |t|
      t.rename :old_column1, :new_column1
      t.rename :old_column2, :new_column2
      ...
    end
  end
end

Then just db:migrate as usual or however you go about your business.

For Rails 4:

While creating a Migration for renaming a column, Rails 4 generates a change method instead of up and down as mentioned in the above section. The generated change method is:

$ > rails g migration ChangeColumnName

which will create a migration file similar to:

class ChangeColumnName < ActiveRecord::Migration
  def change
    rename_column :table_name, :old_column, :new_column
  end
end

I am using RSpec with a Rails engine without issues.

I created my plugin using the following switches: -T --full --dummy-path=spec/dummy.

• -T excludes test/unit
• --full indicates that the plugin is an engine
• --dummy-path is simply so that we don't get a test directory (the default is test/dummy).

From there I used the spec_helper from the "start your engines" article:

# Configure Rails Envinronment
ENV["RAILS_ENV"] = "test"
require File.expand_path("../dummy/config/environment.rb",  __FILE__)

require 'rspec/rails'

ENGINE_RAILS_ROOT=File.join(File.dirname(__FILE__), '../')

# Requires supporting ruby files with custom matchers and macros, etc,
# in spec/support/ and its subdirectories.
Dir[File.join(ENGINE_RAILS_ROOT, "spec/support/**/*.rb")].each {|f| require f }

RSpec.configure do |config|
  config.use_transactional_fixtures = true
end

For the generators. I add a config.generators block to my engine.rb file like so:

module MyEngine
  class Engine < Rails::Engine
    config.generators do |g|
      g.test_framework :rspec, :view_specs => false
    end
  end
end

With that, I'm able to get rspec tests when running a generator like the model generator.

As for the DB, is your database.yml file set up correctly? Did you load the test environment, e.g. rake db:test:clone or rake db:migrate RAILS_ENV=test? My guess is that RSpec can't see your tables because there isn't a test database set up.