canonical-ubuntu-qa team mailing list archive

[Paul Gevers <2058040@xxxxxxxxxxxxxxxxxx>]

Hi,

On 15-03-2024 3:49 p.m., Dave Jones wrote:
> autopkgtest is "clever" about when it resets the testbed betweens tests,
> and this is a Bad Thing (tm) when it breaks assumptions about isolation.

Ironically https://bugs.debian.org/1063533 has a request in the opposite 
direction...

> If the tests are truly isolated, this *should* fail ... but it doesn't.
> Reverse the order of the tests, and of course it does fail. Or add
> another package to the Depends of the first test (so it's a superset of
> the second test) and it fails.

Ack.

> Having spent quite some time failing to debug something, because I'd
> made the faulty assumption that tests were actually isolated, this level
> of "clever" is annoying and should either be removed or at least
> documented, preferably in the man-page so it jumps out at me next time
> I've forgotten this!

Currently I'm in favor of documenting, also because I know that there 
are packages out there that rely on this. It does means that yes, the 
order of the stanza matter.

Paul

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https://bugs.launchpad.net/bugs/2058040

Title:
  autopkgtest doesn't isolate testbeds (sometimes!)

Status in autopkgtest package in Ubuntu:
  New

Bug description:
  autopkgtest is "clever" about when it resets the testbed betweens
  tests, and this is a Bad Thing (tm) when it breaks assumptions about
  isolation. Specifically, in lib/adt_testbed.py under Testbed.reset is
  found the following code:

      def reset(self, deps_new, with_recommends):
          '''Reset the testbed, if possible and necessary'''

          adtlog.debug('testbed reset: modified=%s, deps_installed=%s(r: %s), deps_new=%s(r: %s)' %
                       (self.modified, self.deps_installed, self.recommends_installed,
                        deps_new, with_recommends))
          if 'revert' in self.caps and (
                  self.modified or self.recommends_installed != with_recommends or
                  [d for d in self.deps_installed if d not in deps_new]):
              adtlog.debug('testbed reset')
              pl = self.command('revert', (), 1)
              self._opened(pl)
          self.modified = False

  Paraphrasing, if the test-bed is capable of reversion ('revert' in
  self.caps), and the current test's dependencies (self.deps_installed)
  include packages that are *not* present in the next test's
  dependencies (deps_new), or if the recommends list has changed, then
  *and only then* is the test bed sent the "revert" command which will
  reset it completely (in the case of virt-qemu this restarts the VM
  from scratch). Otherwise it doesn't bother.

  If one makes the (fairly reasonable?) assumption that tests operate in
  isolation to one another this can lead to some ... surprising results.
  Consider the following d/t/control:

    Test-Command: touch /etc/foo
    Depends: build-essential
    Restrictions: isolation-machine, needs-root

    Test-Command: test -e /etc/foo
    Depends: build-essential
    Restrictions: isolation-machine, needs-root

  If the tests are truly isolated, this *should* fail ... but it
  doesn't. Reverse the order of the tests, and of course it does fail.
  Or add another package to the Depends of the first test (so it's a
  superset of the second test) and it fails.

  Having spent quite some time failing to debug something, because I'd
  made the faulty assumption that tests were actually isolated, this
  level of "clever" is annoying and should either be removed or at least
  documented, preferably in the man-page so it jumps out at me next time
  I've forgotten this!

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