[Zope3-dev] testing and savepoints

[Jim Fulton]

Chris Withers wrote:
> Hi all,
> 
> (sorry if some of this is Zope 2 - ish, the thread kinda started here 
> and the underlying bits of this are certainly relevant to Zope 3)
> 
> As you may have guessed by the flurry of mails today, I've been 
> refactoring a 2000 test suite to use layers.
> 
> I was hoping to use savepoints to speed things up...
> 
> Each layer drops a savepoint in setUp and then rolls it back it in 
> tearDown. Likewise, the TestCase's setUp would drop a savepoint and the 
> tearDown would roll back to it.

This is a risky approach.  If you have any software that does actual commits,
you'll be hosed.  I suggest using demo storages instead. Demo storages will
also be faster.

> 
> Sounds great, no?
> 
> Well, no, actually:
> 
> 1. Usual problems of some datamanagers not supporting savepoints. 
> MaildropHost and some of the project's own products datamanagers do. 
> mxODBC does not :-/

Well, they are going to make any approach like this difficult. That's why
I avoid them.

> 2. dropping savepoints is slow.

That hasn't been my experience.

 > Figuring this might be due to saving
> data from the layer each time transaction.savepoint() is called, I 
> thought of getting round this by dropping a savepoint at the end of the 
> layer's setUp method. This did make thing a litte better, but:
> 
> 3. savepoints are really slow :-(

ditto.

> What's the usecase for savepoints? I would have thought this kind of 
> thing would be ideal, but they seem really slow...
> 
> For example, the above test suite takes about 300s to run prior to 
> introducing layers.
> 
> Using savepoints in place of transaction.commit()'s meant it took over 
> 400s! :-(

<shrug>

> So I'm left what the actual use for savepoints is and if they could be 
> made any faster?

See Gary's response.

Jim

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