Re: [boost] trunk vs release

Subject: Re: [boost] trunk vs release
From: Robert Ramey (ramey_at_[hidden])
Date: 2009-05-21 14:12:19

Beman Dawes wrote:
> On Thu, May 21, 2009 at 12:45 PM, Robert Ramey <ramey_at_[hidden]> wrote:
>> This discussion demonstrates what's wrong with the current testing
>> of the trunk.
>>
>> Here is the way it should be done.
>>
>> For each library that is changed, the library version on the trunk
>> should be tested against
>> the release branch. In practice this would work something like the
>> following:
>>
>> On the tester's machine start out with a current image of the release
>> branch.
>> For each library A
>> switch library A's directories to the trunk
>> run tests
>> Restore image to release
>
> Yep, that would often be optimal. Without spending a lot of time
> thinking it through, that sounds roughly like the test-on-demand
> scenario we've often talked about, except with test-on-demand it might
> be any branch, not just trunk, that gets switched to.

Suppose that it was a large loop:

for each library
    switch directories from release to trunk
    run bjam from within that directory
        since bjam tracks dependencies
            if there is no change
                no tests are run
            if there are some changes
                only the dependent tests are run
    switch library directories back to release
on to the next library

Testers would run the whole loop occasionally. My guess is that the total
amount of time required would be similar to running the current test setup
or maybe it would be a lot less.

> One issue, however, is when a library that other libraries depend on
> makes a breaking change.

This should be infrequent and would be a special case.

> In that case a set of libraries have to be
> switched together for testing, and then merged into release at the
> same time.

I don't think so. Note that in the above regimen, such a breaking change
(intentional or not) would appear as a whole slew of failures in dependent
libraries as soon as the breaking change is merged into the release.  At 
that point they
dependent libraries would have to be fixed.  But this doesn't
affect the testing in any way.  It just slogs on with more failures
until they are fixed and the the fixed libraries are merged into
the release.

Robert Ramey

> --Beman
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