Tests within Gem need to test migration generator and apply migrations for tests - ruby

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.

Answer 2

You can do something like this:
I am going to assume you're using ActiveRecord. So in your test helper you should setup a in-memory database:
require 'active_record'
# Connection must be establised before anything else
ActiveRecord::Base.establish_connection(
:adapter => defined?(JRUBY_VERSION) ? 'jdbcsqlite3' : 'sqlite3',
:database => ':memory:'
)
Then invoke the rake task within your test. This would look something like:
require 'rake'
requie File.expand_path('../Rakefile', __FILE__) # you'll need to modify this path to actually point to the Rakefile
Rake::Task['db:migrate'].invoke
The rake taks invocation is untested, but that should point you in the right direction.
The other option would be to just run the command:
%x{rake db:migrate}