Database Cleaner is a set of gems containing 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.
Instead of using the database_cleaner gem directly, each ORM has its own gem. Most projects will only need the database_cleaner-active_record gem:
# Gemfile
group :test do
gem 'database_cleaner-active_record'
endIf you are using multiple ORMs, just load multiple gems:
# Gemfile
group :test do
gem 'database_cleaner-active_record'
gem 'database_cleaner-redis'
endHere is an overview of the databases and ORMs supported by each adapter:
MySQL, PostgreSQL, SQLite, etc
MongoDB
Redis
More details on available configuration options can be found in the README for the specific adapter gem that you're using.
For support or to discuss development please use the Google Group.
The following adapters have been discontinued. Please let us know on the Google Group if you think one of these should be resurrected!
- database_cleaner-data_mapper
- database_cleaner-couch_potato
- database_cleaner-mongo_mapper
- database_cleaner-moped
- database_cleaner-neo4j
require 'database_cleaner/active_record'
DatabaseCleaner.strategy = :truncation
# then, whenever you need to clean the DB
DatabaseCleaner.cleanWith 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 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 DatabaseCleaner.cleaning. So you would have:
require 'database_cleaner/active_record'
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
endAt 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/active_record'
DatabaseCleaner.clean_with :truncation
DatabaseCleaner.strategy = :transaction
# then make the DatabaseCleaner.start and DatabaseCleaner.clean calls appropriatelyFor 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.
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.
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
endYou'll typically discover a feature spec is incorrectly using transaction instead of truncation strategy when the data created in the spec is not visible in the app-under-test.
A frequently occurring example of this is when, after creating a user in a spec, the spec mysteriously fails to login with the user. This happens because the user is created inside of an uncommitted transaction on one database connection, while the login attempt is made using a separate database connection. This separate database connection cannot access the uncommitted user data created over the first database connection due to transaction isolation.
For feature specs using a Capybara driver for an external
JavaScript-capable browser (in practice this is all drivers except
:rack_test), the Rack app under test and the specs do not share a
database connection.
When a spec and app-under-test do not share a database connection, you'll likely need to use the truncation strategy instead of the transaction strategy.
See the suggested config below to temporarily enable truncation strategy for affected feature specs only. This config continues to use transaction strategy for all other specs.
It's also recommended to use append_after to ensure DatabaseCleaner.clean
runs after the after-test cleanup capybara/rspec installs.
require 'capybara/rspec'
#...
RSpec.configure do |config|
config.use_transactional_fixtures = false
config.before(:suite) do
if config.use_transactional_fixtures?
raise(<<-MSG)
Delete line `config.use_transactional_fixtures = true` from rails_helper.rb
(or set it to false) to prevent uncommitted transactions being used in
JavaScript-dependent specs.
During testing, the app-under-test that the browser driver connects to
uses a different database connection to the database connection used by
the spec. The app's database connection would not be able to access
uncommitted transaction data setup over the spec's database connection.
MSG
end
DatabaseCleaner.clean_with(:truncation)
end
config.before(:each) do
DatabaseCleaner.strategy = :transaction
end
config.before(:each, type: :feature) do
# :rack_test driver's Rack app under test shares database connection
# with the specs, so continue to use transaction strategy for speed.
driver_shares_db_connection_with_specs = Capybara.current_driver == :rack_test
unless driver_shares_db_connection_with_specs
# Driver is probably for an external browser with an app
# under test that does *not* share a database connection with the
# specs, so use truncation strategy.
DatabaseCleaner.strategy = :truncation
end
end
config.before(:each) do
DatabaseCleaner.start
end
config.append_after(:each) do
DatabaseCleaner.clean
end
endDatabaseCleaner.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
endIf 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:
require 'database_cleaner/active_record'
DatabaseCleaner.strategy = :truncation
Around do |scenario, block|
DatabaseCleaner.cleaning(&block)
endThis should cover the basics of tear down between scenarios and keeping your database clean.
For more examples see the section "Why?".
Sometimes you need to use multiple ORMs in your application.
You can use DatabaseCleaner to clean multiple ORMs, and multiple databases for those ORMs.
require 'database_cleaner/active_record'
require 'database_cleaner/mongo_mapper'
# How to specify particular orms
DatabaseCleaner[:active_record].strategy = :transaction
DatabaseCleaner[:mongo_mapper].strategy = :truncation
# How to specify particular databases
DatabaseCleaner[:active_record, db: :two]
# You may also pass in the model directly:
DatabaseCleaner[:active_record, db: ModelWithDifferentConnection]Usage beyond that remains the same with DatabaseCleaner.start calling any setup on the different configured databases, and DatabaseCleaner.clean executing afterwards.
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.
DatabaseCleaner comes with safeguards against:
- Running in production (checking for
ENV,APP_ENV,RACK_ENV, andRAILS_ENV) - Running against a remote database (checking for a
DATABASE_URLthat does not includelocalhost,.localor127.0.0.1)
Both safeguards can be disabled separately as follows.
Using environment variables:
export DATABASE_CLEANER_ALLOW_PRODUCTION=true
export DATABASE_CLEANER_ALLOW_REMOTE_DATABASE_URL=true
In Ruby:
DatabaseCleaner.allow_production = true
DatabaseCleaner.allow_remote_database_url = trueIn Ruby, a URL allowlist can be specified. When specified, DatabaseCleaner will only allow DATABASE_URL to be equal
to one of the values specified in the url allowlist like so:
DatabaseCleaner.url_allowlist = ['postgres://postgres@localhost', 'postgres://foo@bar']Allowlist elements are matched with case equality (===), so regular expressions or procs may be used:
DatabaseCleaner.url_allowlist = [
%r{^postgres://postgres@localhost}, # match any db with this prefix
proc {|uri| URI.parse(uri).user == "test" } # match any db authenticating with the 'test' user
]See HISTORY for details.
See LICENSE for details.
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