database_cleaner/adapters/database_cleaner-active_record

Database Cleaner Adapter for ActiveRecord

Clean your ActiveRecord databases with Database Cleaner.

See https://github.com/DatabaseCleaner/database_cleaner for more information.

Installation

# Gemfile
group :test do
  gem 'database_cleaner-active_record'
end

Supported Strategies

Here is an overview of the supported strategies:

Truncation	Transaction	Deletion
Yes	Yes	Yes

(Default strategy is denoted in bold)

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

What strategy is fastest?

For the SQL libraries the fastest option will be to use :transaction as transactions are simply rolled back. If you can use this strategy you should. However, if you wind up needing to use multiple database connections in your tests (i.e. your tests run in a different process than your application) then using this strategy becomes a bit more difficult. You can get around the problem a number of ways.

One common approach is to force all processes to use the same database connection (common ActiveRecord hack) however this approach has been reported to result in non-deterministic failures.

Another approach is to have the transactions rolled back in the application's process and relax the isolation level of the database (so the tests can read the uncommitted transactions).

An easier, but slower, solution is to use the :truncation or :deletion strategy.

So what is fastest out of :deletion and :truncation? Well, it depends on your table structure and what percentage of tables you populate in an average test. The reasoning is out of the scope of this README but here is a good SO answer on this topic for Postgres.

Some people report much faster speeds with :deletion while others say :truncation is faster for them. The best approach therefore is it try all options on your test suite and see what is faster.

If you are using ActiveRecord then take a look at the additional options available for :truncation.

Configuration options

ORM	How to access	Notes
Active Record	DatabaseCleaner[:active_record]	Connection specified as :symbol keys, loaded from config/database.yml. You may also pass in the ActiveRecord model under the :model key.

Additional ActiveRecord options for Truncation

The following options are available for ActiveRecord's :truncation strategy only for MySQL and Postgres.

• :pre_count - When set to true this will check each table for existing rows before truncating it. This can speed up test suites when many of the tables to be truncated are never populated. Defaults to :false. (Also, see the section on What strategy is fastest?)
• :reset_ids - This only matters when :pre_count is used, and it will make sure that a tables auto-incrementing id is reset even if there are no rows in the table (e.g. records were created in the test but also removed before DatabaseCleaner gets to it). Defaults to true.

The following option is available for ActiveRecord's :truncation and :deletion strategy for any DB.

• :cache_tables - When set to true the list of tables to truncate or delete from will only be read from the DB once, otherwise it will be read before each cleanup run. Set this to false if (1) you create and drop tables in your tests, or (2) you change Postgres schemas (ActiveRecord::Base.connection.schema_search_path) in your tests (for example, in a multitenancy setup with each tenant in a different Postgres schema). Defaults to true.

Common Errors

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

For ActiveRecord, you add the following parameter in your database.yml file:

test:
  adapter: postgresql
  # ...
  min_messages: WARNING  

COPYRIGHT

See [LICENSE] for details.