On 12 Jan 2009, at 17:36, Ben Mabey wrote:
On 1/12/09 7:09 AM, Matt Wynne wrote:
Hi all,
We did a spike last week to de-couple our view and controller tests
from the database, using NullDb. It didn't go too well. I realise
that this plugin isn't part of RSpec, but I thought others on this
list might have experiences to share.
Here's a summary of my colleague's investigations:
I installed the plugin from http://github.com/jakehow/nulldb/tree/master
Changed spec/spec_helper to set
"ActiveRecord::Base.establish_connection(:adapter => :nulldb)" by
default.
The specs that complained of the lack of db, I included a
before(all)
that changed the connection to the test database (include
NeedsDatabase - copied from Ben Mabey's Functional module)
By default, I also included the db for all models (config.include
NeedsDatabase, :type => :model)
Running spec spec/views with or without nulldb takes about the same
time (a couple of seconds less with nulldb). However, running "rake
spec" with nulldb takes 10 times longer!!
Another weird thing was that three tests failed in the controllers
(venues and concerts) in a very strange way, even when I included
the
NeedsDatabase in the tests that needed it. The weird bit is, when I
run: "spec spec/controllers/venues_controller_spec.rb" it doesn't
fail. But when I run: "spec spec/controllers/
users_controller_spec.rb
spec/controllers/venues_controller_spec.rb" It does fail... That is,
the user_controller test is influencing the results of the
venue_controller test!
The same weird behaviour happens in lib/sk/find
This made me had to include NeedsDatabase for all lib and
controllers
tests as well.
The barrier for us was the shockingly poor performance of 'rake
spec' on the view specs - it really means we just can't use it, and
actually only barely improved the performance of the specs at all.
I was disappointed that the view specs didn't get any faster. My
guess is that stub_model is the problem - as it has to do quite a
bit of work to set up the attributes on the models.
So, can anyone tell us what we might have been doing wrong? Or did
I just have unrealistic expectations of how this might help?
Matt Wynne
http://blog.mattwynne.net
http://www.songkick.com
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Hey Matt,
I had similar experiences when I started using NullDB. I think that
the reason why the overall spec suite runs slow is AR is switching
from one adapter to another, and in the case of the mysql one it
probably is relatively expensive to set up a new connection.
Switching over to using NullDB on an existing project of any sizable
size is going to be large task IMO. On my last project we started
using NullDB by default and the result has been very worthwhile and
noticeable. In this project DB connectivity was the exception, not
the norm (even on our model specs) and so that is why I created a
module that would turn on the DB temporarily. In your case the
opposite approach may be needed.
Going back to the problem at hand... Based on the email you are
using a module like this:
unless Object.const_defined?(:NeedsDatabase)
share_as :NeedsDatabase do
before :all do
ActiveRecord::Base.establish_connection(:test)
end
after :all do
ActiveRecord::Base.establish_connection(:adapter => :nulldb)
end
end
end
Since you are including this on all of your model specs (and more)
you are incurring the setup and teardown cost of the DB connection
repeatedly. Like I said, you may want to adopt the opposite policy
of turning it off temporarily... You could also make the the
changing smarter by only changing it when you need to.. something
like:
share_as :NeedsDatabase do
before :all do
ActiveRecord::Base.establish_connection(:test) if
ActiveRecord::Base.connection.class.to_s =~ /NullDB/
end
end
share_as :DontNeedDatabase do
before :all do
ActiveRecord::Base.establish_connection(:adapter => :nulldb)
unless ActiveRecord::Base.connection.class.to_s =~ /NullDB/
end
end
With this approach you would need to specify whether or not to use
the DB for each example group... just a thought. Of course, an even
better solution would be to somehow modify AR to maintain an active
connection to the real DB even when it isn't the active adapter.
re: the view specs
I wouldn't expect to see too much gain here. The big win for
nullDB is in models IMO. Of course, having it on the view and
controller specs helps prevent accidental DB calls.
re: the random controller spec failures
I only guess is that you are somehow relying on the DB in your
controller specs. I did this too in my controllers when I called
class methods on models that would get a list from the DB... I can't
really help without seeing any specs though.
I hope this helps and you can find a suitable policy on how to
manage the connections/adapters. Just ask if you have any other
questions.
-Ben
Thanks Ben. I had a brief look at the AR code and it did appear to be
caching the adapters so I'd assumed the changeover wasn't expensive,
but it did feel like something like that, so that's probably it.
Ho hum. No quick wins for speeding up our specs then!
Matt Wynne
http://blog.mattwynne.net
http://www.songkick.com
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