NullDB is a Rails database connection adapter that interprets common
database operations as no-ops. It is the Null Object pattern as
applied to database adapters.
Once installed, NullDB can be used much like any other ActiveRecord
ActiveRecord::Base.establish_connection :adapter => nulldb
NullDB needs to know where you keep your schema file in order to
reflect table metadata. By default it looks in
RAILS_ROOT/db/schema.rb. You can override that by setting the
ActiveRecord::Base.establish_connection :adapter => nulldb,
:schema => foo/myschema.rb
There is a helper method included for configuring RSpec sessions to
use NullDB. Just put the following in your spec/spec_helper.rb:
Spec::Runner.configure do |config|
You can also experiment with putting NullDB in your database.yml:
However, due to the way Rails hard-codes specific database adapters
into its standard Rake tasks, you may find that this generates
unexpected and difficult-to-debug behavior. Workarounds for this are
NullDB is intended to assist in writing fast database-independant unit
tests for ActiveRecord classes. For why you would want to test your
models without the database, see:
It works. At the time of writing both ARBS and UnitRecord were
not working for me out of the box with Rails 2.0.
It avoids monkey-patching as much as possible. Rather than
re-wiring the secret inner workings of ActiveRecord (and thus being
tightly coupled to those inner workings), NullDB implements the
same [semi-]well-documented public interface that the other standard
database adapters, like MySQL and SQLServer, implement.
UnitRecord takes the approach of eliminating database interaction
in tests by turning almost every database interaction into an
exception. NullDB recognizes that ActiveRecord objects typically
can’t take two steps without consulting the database, so instead it
turns database interactions into no-ops.
One concrete advantage of this null-object pattern design is that it
is possible with NullDB to test +after_save+ hooks. With NullDB, you
can call +#save+ and all of the usual callbacks will be called - but
nothing will be saved.
- It is not an in-memory database. Finds will not work. Neither
will #reload, currently.
- It has only the most rudimentery schema/migration support. Complex
migrations will probably break it.
- Lots of other things probably don’t work. Patches welcome!
NullDB was written by Avdi G. mailto:[email protected]
- Version 0.0.1 (2007-02-18)
- Initial Release