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Strategies for cleaning databases in Ruby. Can be used to ensure a clean state for testing.

README.textile

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
ActiveRecord Yes Yes Yes
DataMapper Yes Yes No
CouchPotato Yes No No
MongoMapper Yes No No
Mongoid Yes No No
Sequel Yes Yes 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.

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

Dependencies

Because database_cleaner supports multiple ORMs, it doesn’t make sense to include all the dependencies
for each one in the gemspec. However, the DataMapper adapter does depend on dm-transactions. Therefore,
if you use DataMapper, you must include dm-transactions in your Gemfile/bundle/gemset manually.

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

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?”

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

Common Errors

DatabaseCleaner is trying to use the wrong ORM

DatabaseCleaner has an autodetect mechanism where if you do not explicitly define your ORM it will use the first ORM it can detect that is loaded. Since ActiveRecord is the most common ORM used that is the first one checked for. Sometimes other libraries (e.g. ActiveAdmin) will load other ORMs (e.g. ActiveRecord) even though you are using a different ORM. This will result in DatabaseCleaner trying to use the wrong ORM (e.g. ActiveRecord) unless you explicitly define your ORM like so:

  # How to setup your ORM explicitly
  DatabaseCleaner[:mongoid].strategy = :truncation

STDERR is being flooded when using Postgres

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

Debugging

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

COPYRIGHT

Copyright © 2009 Ben Mabey. See LICENSE for details.

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