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, CouchPotato, Ohm and Redis 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 |
Redis | Yes | No | No |
Ohm | Yes | No | No |
Neo4j | Yes | Yes* | Yes* |
Truncation and Deletion strategies for Neo4j will just delete all nodes and relationships from the database.
Driver | Truncation | Transaction | Deletion |
---|---|---|---|
Mongo | Yes | No | No |
Moped | Yes | No | No |
(Default strategy for each library is denoted in bold)
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.
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
.
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]}
With Ohm and Redis, :only
and :except
take a list
of strings to be passed to keys).
(I should point out the truncation strategy will never truncate your schema_migrations table.)
Some strategies need to be started before tests are run (for example the
:transaction
strategy needs to know to open up a transaction).
This can be accomplished by calling DatabaseCleaner.start
at
the beginning of the run, or by running the tests inside a block to
Database.cleaning
. 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 # OR DatabaseCleaner.cleaning do dirty_the_db end
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
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 you create and drop tables in your tests. Defaults to
true
.
RSpec Example¶ ↑
RSpec.configure do |config| config.before(:suite) do DatabaseCleaner.strategy = :transaction DatabaseCleaner.clean_with(:truncation) end config.around(:each) do |example| DatabaseCleaner.cleaning do example.run end end end
Minitest Example¶ ↑
DatabaseCleaner.strategy = :transaction class MiniTest::Spec before :each do DatabaseCleaner.start end after :each do DatabaseCleaner.clean end end # with the minitest-around gem, this may be used instead: class Minitest::Spec around do |tests| DatabaseCleaner.cleaning(&tests) end end
Cucumber Example¶ ↑
If you're using Cucumber with Rails, just use the generator that ships with cucumber-rails, and that will create all the code you need to integrate DatabaseCleaner into your Rails project.
Otherwise, to add DatabaseCleaner to
your project by hand, create a file
features/support/database_cleaner.rb
that looks like this:
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 Around do |scenario, block| DatabaseCleaner.cleaning(&block) 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}] # You may also pass in the model directly: DatabaseCleaner[:active_record,{:model => ModelWithDifferentConnection}]
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 . You may also pass in the ActiveRecord model under the :model key. |
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 databases supported for Mongoid 3. Specify DatabaseCleaner[:mongoid, {:connection => :db_name}] |
Moped | DatabaseCleaner[:moped] |
It is necessary to configure database name with DatabaseCleaner[:moped].db = db_name otherwise name `default` will be used. |
Couch Potato | DatabaseCleaner[:couch_potato] |
Multiple connections not yet supported |
Sequel | DatabaseCleaner[:sequel] |
Multiple databases supported; specify DatabaseCleaner[:sequel, {:connection => Sequel.connect(uri)}] |
Redis | DatabaseCleaner[:redis] |
Connection specified as Redis URI |
Ohm | DatabaseCleaner[:ohm] |
Connection specified as Redis URI |
Neo4j | DatabaseCleaner[:neo4j] |
Database type and path(URI) DatabaseCleaner[:neo4j, connection: {type: :server_db, path: 'http://localhost:7475'}]. |
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.
After copying and pasting code to do this several times I decided to package it up as a gem and save everyone a bit of time.
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
For ActiveRecord, you add the following parameter in your database.yml file:
test: adapter: postgresql # ... min_messages: WARNING
Nothing happens in JRuby with Sequel using transactions¶ ↑
Due to an inconsistency in JRuby's implementation of Fibers, Sequel
gives a different connection to DatabaseCleaner.start
than is
used for tests run between .start
and .clean
.
This can be worked around by running your tests in a block like
DatabaseCleaner.cleaning { run_my_tests }
instead, which does
not use Fibers.
Model fails to load with Neo4j using transactions¶ ↑
When you are using neo4j gem it creates schema and reads indexes upon loading models. These operations can't be done during a transaction. You have to preload your models before DatabaseCleaner starts a transaction.
Add to your rails_helper or spec_helper after requiring database_cleaner:
require 'database_cleaner' Dir["#{Rails.root}/app/models /*.rb"].each do |model| load model end
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 © 2014 Ben Mabey. See LICENSE for details.