Question

I’m working on a Gem that contains a migration generator and a bunch of models, classes, etc that utilize the tables created as part of the migration.

Although testing the migration generator itself is easy enough – there’s loads of tutorials around for getting that done, what i’m trying to work out is how to actually run the migration on the test DB so I can later test how the gem interacts with the test data?

Since the gem doesn’t have a schema.rb, I wasn’t sure how to go about doing it.

Answer 1

This is how I run migrations in code;

  ActiveRecord::Base.establish_connection(:adapter => "sqlite3", :database => ":memory:")
  ActiveRecord::Migration.verbose = false

  @migration  = Class.new(ActiveRecord::Migration) do

    def change
      create_table :users, :force => true do |t|
        t.string     :roles_mask
      end
      create_table :user_without_roles, :force => true do |t|
        t.string     :roles_mask
      end
      create_table :user_without_role_masks, :force => true do |t|
      end
    end

  end

  @migration.new.migrate(:up)

If you have a string containing your generated migration you could do something like this in your test setup;

  ActiveRecord::Base.establish_connection(:adapter => "sqlite3", :database => ":memory:")
  ActiveRecord::Migration.verbose = false

  # Or however you intend to grab the output of the migration generator
  migration_string = ERB.new(File.read(<file name here>)).result

  migration  = Class.new(ActiveRecord::Migration)
  migration.class_eval(migration_string)
  migration.new.migrate(:up)

That should give you a migrated database using the migration you’ve generated.