Database Cleaner

Database Cleaner is a set of strategies for cleaning your database in Ruby.
The original use case was to ensure a clean state during tests. Each strategy
is a small amount of code but is code that is usually needed in any ruby app
that is testing with a database.

ActiveRecord, DataMapper, Sequel, MongoMapper, Mongoid, and CouchPotato are supported.

Here is an overview of the strategies supported for each library:

ORM	Truncation	Transaction	Deletion	Removal
ActiveRecord	Yes	Yes	Yes	Yes
DataMapper	Yes	Yes	No	Yes
CouchPotato	Yes	No	No	No
MongoMapper	Yes	No	No	No
Sequel	Yes	Yes	No	No

(Default strategy for each library is denoted in bold)

The ActiveRecord :deletion strategy is useful for when the :truncation strategy causes
locks (as reported by some Oracle DB users). The :deletion option has been reported to
be faster than :truncation in some cases as well. In general, the best approach is to use
:transaction since it is the fastest.

Database Cleaner also includes a null strategy (that does no cleaning at all) which can be used
with any ORM library. You can also explicitly use it by setting your strategy to nil.

The addition of the :removal strategy is typically for use with external web applications
where the web app cannot run within a transaction and it is desirable to remove records from
the database after a cucumber scenario has completed and where deleting all records from tables
(as in the Deletion strategy) is not desirable (for example, if you want to start with known
data in the database.)

For support or to discuss development please use the Google Group.

How to use

  require 'database_cleaner'
  DatabaseCleaner.strategy = :truncation

  # then, whenever you need to clean the DB
  DatabaseCleaner.clean

With the :truncation strategy you can also pass in options, for example:

  DatabaseCleaner.strategy = :truncation, {:only => %w[widgets dogs some_other_table]}

  DatabaseCleaner.strategy = :truncation, {:except => %w[widgets]}

(I should point out the truncation strategy will never truncate your schema_migrations table.)

Some strategies require that you call DatabaseCleaner.start before calling clean
(for example the :transaction one needs to know to open up a transaction). So
you would have:

  require 'database_cleaner'
  DatabaseCleaner.strategy = :transaction

  DatabaseCleaner.start # usually this is called in setup of a test
  dirty_the_db
  DatabaseCleaner.clean # cleanup of the test

At times you may want to do a single clean with one strategy. For example, you may want
to start the process by truncating all the tables, but then use the faster transaction
strategy the remaining time. To accomplish this you can say:

  require 'database_cleaner'
  DatabaseCleaner.clean_with :truncation
  DatabaseCleaner.strategy = :transaction
  # then make the DatabaseCleaner.start and DatabaseCleaner.clean calls appropriately

Removal Strategy

The :removal strategy is useful if you want to work with a database with existing data and loading the data set would be too slow to repeat at each clean. This can also be useful if you are testing a remote web application in another language that cannot share a database connection and make use of the :transaction strategy.

This strategy supports both ActiveRecord and DataMapper ORMs.

For example:

  require 'database_cleaner'
  DatabaseCleaner.strategy = :removal

  DatabaseCleaner.start

  # removing an object at clean
  user = User.create
  user.save
  DatabaseCleaner.mark_for_removal user

  # setup removal in FactoryGirl:
  FactoryGirl.define do
    factory :user do
      name "Joe Bloggs"
      after_create { |user| DatabaseCleaner.mark_for_removal user }
    end
  end
  # this object will also be removed at clean
  user = FactoryGirl.create :user

  # you can also undo a record change at clean
  account = Account.find_the_account
  original_balance = account.balance
  DatabaseCleaner.at_removal do
    account.balance = original_balance
    account.save
  end
  perform_some_action_that_changes_the_balance_in account

  # destroy the 2 users created above and revert the change to the account balance:
  DatabaseCleaner.start

RSpec Example

RSpec.configure do |config|

  config.before(:suite) do
    DatabaseCleaner.strategy = :transaction
    DatabaseCleaner.clean_with(:truncation)
  end

  config.before(:each) do
    DatabaseCleaner.start
  end

  config.after(:each) do
    DatabaseCleaner.clean
  end

end

Cucumber Example

Add this to your features/support/env.rb file:

begin
  require 'database_cleaner'
  require 'database_cleaner/cucumber'
  DatabaseCleaner.strategy = :truncation
rescue NameError
  raise "You need to add database_cleaner to your Gemfile (in the :test group) if you wish to use it."
end

A good idea is to create the before and after hooks to use the DatabaseCleaner.start and DatabaseCleaner.clean methods.

Inside features/support/hooks.rb:

Before do
  DatabaseCleaner.start
end

After do |scenario|
  DatabaseCleaner.clean
end

This should cover the basics of tear down between scenarios and keeping your database clean.
For more examples see the section “Why?”

Common Errors

In rare cases DatabaseCleaner will encounter errors that it will log. By default it uses STDOUT set to the ERROR level but you can configure this to use whatever Logger you desire. Here’s an example of using the Rails.logger in env.rb:

  DatabaseCleaner.logger = Rails.logger

If you are using Postgres and have foreign key constraints, the truncation strategy will cause a lot of extra noise to appear on STDERR (in
the form of “NOTICE truncate cascades” messages). To silence these warnings set the following log level in your postgresql.conf file:

  client_min_messages = warning

How to use with multiple ORM’s

Sometimes you need to use multiple ORMs in your application. You can use DatabaseCleaner to clean multiple ORMs, and multiple connections for those ORMs.

  #How to specify particular orms
  DatabaseCleaner[:active_record].strategy = :transaction
  DatabaseCleaner[:mongo_mapper].strategy = :truncation

  #How to specify particular connections
  DatabaseCleaner[:active_record,{:connection => :two}]

Usage beyond that remains the same with DatabaseCleaner.start calling any setup on the different configured connections, and DatabaseCleaner.clean executing afterwards.

Configuration options

ORM	How to access	Notes
Active Record	DatabaseCleaner[:active_record]	Connection specified as :symbol keys, loaded from config/database.yml
Data Mapper	DatabaseCleaner[:data_mapper]	Connection specified as :symbol keys, loaded via Datamapper repositories
Mongo Mapper	DatabaseCleaner[:mongo_mapper]	Multiple connections not yet supported
Mongoid	DatabaseCleaner[:mongoid]	Multiple connections not yet supported
Couch Potato	DatabaseCleaner[:couch_potato]	Multiple connections not yet supported
Sequel	DatabaseCleaner[:sequel]	?

Why?

One of my motivations for writing this library was to have an easy way to
turn on what Rails calls “transactional_fixtures” in my non-rails
ActiveRecord projects. For example, Cucumber ships with a Rails world that
will wrap each scenario in a transaction. This is great, but what if you are
using ActiveRecord in a non-rails project? You used to have to copy-and-paste
the needed code, but with DatabaseCleaner you can now say:

  #env.rb
  require 'database_cleaner'
  require 'database_cleaner/cucumber'
  DatabaseCleaner.strategy = :transaction

Now lets say you are running your features and it requires that another process be
involved (i.e. Selenium running against your app’s server.) You can simply change
your strategy type:

  #env.rb
  require 'database_cleaner'
  require 'database_cleaner/cucumber'
  DatabaseCleaner.strategy = :truncation

You can have the best of both worlds and use the best one for the job:

  #env.rb

  require ‘database_cleaner’

  require ‘database_cleaner/cucumber’

  DatabaseCleaner.strategy = (ENV[‘SELENIUM’] == ‘true’) ? :truncation : :transaction

COPYRIGHT

Copyright © 2009 Ben Mabey. See LICENSE for details.
Copyright © 2012 Matt Connolly. See LICENSE for details.