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KIR

2011-Oct-15 20:19 UTC

A proper way to test that database is not accessed?

Hello,

  Previously I''ve had a helper assert_no_database like this:

  def assert_no_database
    old_con = ActiveRecord::Base.remove_connection
    begin
      yield
    ensure
      ActiveRecord::Base.establish_connection old_con
    end
  end

  But it doesn''t work in Rails 3.1.1 anymore (due to the following
change:
https://github.com/rails/rails/issues/2820)

  Any suggestion for a proper way to check that a block of code doesn''t
access database?

  Thanks,
  KIR

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Mislav Marohnić

2011-Oct-15 22:01 UTC

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Re: A proper way to test that database is not accessed?

On Oct 15, 2011, at 10:19 PM, KIR wrote:
> Any suggestion for a proper way to check that a block of code
doesn''t access database?
How about:

  ActiveRecord::Base.establish_connection Rails.env

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KIR

2011-Oct-16 06:35 UTC

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Re: A proper way to test that database is not accessed?

>
>  ActiveRecord::Base.establish_connection Rails.env
>
   I don''t quite understand what do you mean here?

   My problem is that code like the following results in
ConnectionNotEstablished exception (though it worked in 3.1):

model = Task.first
old_con = ActiveRecord::Base.remove_connection
model.any_attr_name  # check no access to DB
ActiveRecord::Base.establish_connection old_con



>
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Mislav Marohnić

2011-Oct-16 15:52 UTC

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Re: A proper way to test that database is not accessed?

On Oct 16, 2011, at 8:35 AM, KIR wrote:
>  ActiveRecord::Base.establish_connection Rails.env
> 
>    I don''t quite understand what do you mean here?
I know what your problem is. If because of changes to Rails reconnecting to the
db by using the old connection doesn''t work, then I suggested that you
give up on using the old connection and just instruct AR to connect as if the
application was just booting up. Have you tried what I suggested at all? Are you
having the same problem?

  def without_database_connection
    ActiveRecord::Base.remove_connection
    begin
      yield
    ensure
      ActiveRecord::Base.establish_connection Rails.env
    end
  end

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KIR

2011-Oct-16 16:22 UTC

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Re: A proper way to test that database is not accessed?

>
> I know what your problem is. If because of changes to Rails reconnecting to
> the db by using the old connection doesn''t work, then I suggested
that you
> give up on using the old connection and just instruct AR to connect as if
> the application was just booting up. Have you tried what I suggested at
all?
> Are you having the same problem?
>
>   def without_database_connection
>     ActiveRecord::Base.remove_connection
>     begin
>       yield
>     ensure
>       ActiveRecord::Base.establish_connection Rails.env
>     end
>   end
>
>   Thanks Mislav, I tried your suggestion, but it doesn''t work.

   My actual problem is not about restoring the connection (but thanks for
the tip, I may need it eventually).
   It is about the fact that I _always_ get exception when I''m trying
to
access model attributes when connection was removed with remove_connection
(i.e. I get exception in the yield part).

   BTW, have you tried your helper on Rails 3.1.1?

   Thanks,
   KIR



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Software Engineer & Starter


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Mislav Marohnić

2011-Oct-16 17:19 UTC

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Re: A proper way to test that database is not accessed?

On Oct 16, 2011, at 6:22 PM, KIR wrote:
>    BTW, have you tried your helper on Rails 3.1.1?
I haven''t tried my code, I just pulled it out of the air. Sorry that I
misunderstood your problem – I thought it was about reconnecting.

I have the feeling that others also didn''t get what you were saying;
people who got notified about your comment on the issue tracker probably thought
that you have a problem in your custom helper.

The most important thing right now to establish whether this is a real bug or
not. The behavior which you relied on before the offending change might not have
been intentional. It''s possible that you might be testing wrong things
in your application.

You should describe what are you doing inside the no connection block. (You
mentioned using attribute accessors, but in order to generate these accessors,
AR must have an open connection so it can fetch information about table
columns.) Describe shortly what you were expecting to get and how the new
behavior surprises you and breaks your tests.

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KIR

2011-Oct-16 17:42 UTC

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Re: A proper way to test that database is not accessed?

>
> You should describe what are you doing inside the no connection block. (You
> mentioned using attribute accessors, but in order to generate these
> accessors, AR must have an open connection so it can fetch information
about
> table columns.) Describe shortly what you were expecting to get and how the
> new behavior surprises you and breaks your tests.
>
   Basically, I have a test that I don''t have N+1 problem when
collecting
data.
   I do something like this:

   # in the production, this may generate hundreds of items (which have own
associations)
   sub_model_items = model.preload_subitems

   assert_no_database {
     json = sub_model_items.build_json
   }

   What I''m trying to test - that my code doesn''t perform SQL
operations
when building json, i.e. all data should be preloaded.

   Thanks,
   KIR


-- 

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Software Engineer & Starter


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Mislav Marohnić

2011-Oct-16 17:58 UTC

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Re: A proper way to test that database is not accessed?

On Oct 16, 2011, at 7:42 PM, KIR wrote:> What I''m trying to test - that my code doesn''t perform
SQL operations when building json, i.e. all data should be preloaded.
That''s a perfectly valid thing to test. Looks like it might be a
regression. I suggest that you update the issue (where you commented on) with
this information, including your own code related to this and provide a stack
trace pasted into a Gist.

Until you have a solution for this problem, I suggest testing this another way.
In will_paginate, I subscribe to all SQL queries performed and then I check them
in tests to see whether there have been too many executed during a particular
test.


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KIR

2011-Oct-16 19:08 UTC

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Re: A proper way to test that database is not accessed?

>
> What I''m trying to test - that my code doesn''t perform
SQL operations when
> building json, i.e. all data should be preloaded.
>
>
> That''s a perfectly valid thing to test. Looks like it might be a
> regression. I suggest that you update the issue (where you commented on)
> with this information, including your own code related to this and provide
a
> stack trace pasted into a Gist.
>
> Until you have a solution for this problem, I suggest testing this another
> way. In will_paginate, I subscribe to all SQL queries
performed<https://github.com/mislav/will_paginate/blob/d56a8436/spec/finders/activerecord_test_connector.rb#L5-23>
and
> then I check them in tests to see whether there have been too many executed
> during a particular test.
>
>    Thanks a lot for the hint, will investigate it.
    May be, I''ll be able to rewrite my assert_no_database assertion
using
its approach.

    All the best,
    KIR

>
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Kirill (KIR) Maximov

Software Engineer & Starter


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Will Bryant

2011-Oct-17 02:54 UTC

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Re: A proper way to test that database is not accessed?

On 17/10/2011, at 08:08 , KIR wrote:
> 
>     Thanks a lot for the hint, will investigate it. 
>     May be, I''ll be able to rewrite my assert_no_database
assertion using its approach.
There''s assert_queries/assert_no_queries in the test case support code,
which sound quite similar to what you want.  But it needs a subscriber
implementation (such as Mislav was talking about for will_paginate), which you
need to feed into the global variable that the assertions check.

Rails has a subscriber implementation for its own tests, but it isn''t
exposed.  IMHO it would be great it did, so we could just instantiate that in
app test code without having to copy it in (it''s somewhat
version-specific).

Have a look at activerecord/test/cases/helper.rb to see how it works.  The
assertions that use it are defined in
activerecord/lib/active_record/test_case.rb, so they are exposed, which
doesn''t make much sense at the moment.

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KIR

2011-Oct-22 09:24 UTC

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Re: A proper way to test that database is not accessed?

Will, Mislav, thanks for all your help!

I''ve used subscriber to implement my assert_no_database helper. When
asserted block of code performs any SQL requests, these requests are
included into test output: https://gist.github.com/1305807

 Thanks again!
 KIR



On 17 October 2011 04:54, Will Bryant <will.bryant@gmail.com> wrote:
> On 17/10/2011, at 08:08 , KIR wrote:
>
> >
> >     Thanks a lot for the hint, will investigate it.
> >     May be, I''ll be able to rewrite my assert_no_database
assertion using
> its approach.
>
> There''s assert_queries/assert_no_queries in the test case support
code,
> which sound quite similar to what you want.  But it needs a subscriber
> implementation (such as Mislav was talking about for will_paginate), which
> you need to feed into the global variable that the assertions check.
>
> Rails has a subscriber implementation for its own tests, but it
isn''t
> exposed.  IMHO it would be great it did, so we could just instantiate that
> in app test code without having to copy it in (it''s somewhat
> version-specific).
>
> Have a look at activerecord/test/cases/helper.rb to see how it works.  The
> assertions that use it are defined in
> activerecord/lib/active_record/test_case.rb, so they are exposed, which
> doesn''t make much sense at the moment.
>
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>

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Rails core - Oct 2011 - A proper way to test that database is not accessed?

A proper way to test that database is not accessed?

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Re: A proper way to test that database is not accessed?

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Re: A proper way to test that database is not accessed?

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