database_cleaner/README.textile

h1. 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             |
| 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@.

h2. How to use

<pre>
  require 'database_cleaner'
  DatabaseCleaner.strategy = :truncation

  # then, whenever you need to clean the DB
  DatabaseCleaner.clean
</pre>

With the :truncation strategy you can also pass in options, for example:
<pre>
  DatabaseCleaner.strategy = :truncation, {:only => %w[widgets dogs some_other_table]}
</pre>

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

(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:

<pre>
  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
</pre>

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:

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

h3. RSpec Example

<pre>
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
</pre>

h3. Cucumber Example

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

<pre>
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
</pre>

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:

<pre>
Before do
  DatabaseCleaner.start
end

After do |scenario|
  DatabaseCleaner.clean
end
</pre>

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

h2. 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:

<pre>
  DatabaseCleaner.logger = Rails.logger
</pre>

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:

<pre>
  client_min_messages = warning
</pre>

h2. 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.

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

  #How to specify particular connections

  # with DataMapper you pass in the name of the repository
  DatabaseCleaner[:data_mapper,{:connection => :my_other_repository}]

  # With ActiveRecord you pass in the model whose #connection DataCleaner should use
  DatabaseCleaner[:active_record,{:connection => Widget}]
  DatabaseCleaner[:active_record,{:connection => "Widget"}] # You may pass in the model as a String in case you need/want to delay loading.
</pre>

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]        | ?                                                                        |

h2. 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:

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

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:

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

You can have the best of both worlds and use the best one for the job:
<pre>
  #env.rb
  require 'database_cleaner'
  require 'database_cleaner/cucumber'
  DatabaseCleaner.strategy = (ENV['SELENIUM'] == 'true') ? :truncation : :transaction
</pre>

h2. COPYRIGHT

Copyright (c) 2009 Ben Mabey. See LICENSE for details.