[Avocado-devel] RFC: Guidelines for categorizing tests

[Ademar Reis]

On Wed, May 17, 2017 at 05:49:36PM -0400, Cleber Rosa wrote:
> Introduction
> ============
> 
> Avocado allows users to select tests to run based on free form "tags".
> These tags are given as "docstring directives", that is, special
> entries on a class or function docstring.
> 
> As a user of an Avocado based test suite, I'd see value in not **having**
> to look at all the test tags before realizing that to not run tests that
> require "super user" permissions I should run::
> 
>   $ avocado run test.py --filter-by-tags=-root
> 
> Instead of::
> 
>   $ avocado run test.py --filter-by-tags=-privileged
> 
> Not even that, by having different tests as part of the same job,
> the following very odd sequence of command line options may be
> needed::
> 
>   $ avocado run test.py test2.py --filter-by-tags=-root,-privileged
> 
> So the goal here is to let users familiar with a given Avocado based
> test, to have fair expectations when running another Avocado based
> tests.
> 
> This was initially going to be a documentation update, but I felt that
> it was not fair to make a formal proposal without without some initial
> brainstorming.
> 
> Proposal
> ========
> 
> To set the tone for my proposal, I'd like to make most things simple
> and easy, while allowing for "everything else" to be doable.
> 
> My general impression is that higher level information about the test
> itself and its requirements are going to be the most commonly used
> tags, so they must be easily set.  Some examples follow.
> 
> Simple (standalone) tags
> ------------------------
> 
> Tags by functional area:
> 
>  * cpu - Exercises a system's CPU
>  * net - Exercises a system's network devices or networking stack
>  * storage - Exercises a system's local storage
>  * fs - Exercises a system's file system
> 
> Tags by architecture:
> 
>  * x86_64 - Requires a x86_64 architecture
>  * ppc64 - Requries a ppc64
> 
> Tags by access privileges:
> 
>  * privileged - requires the test to be run with the most privileged,
>    unrestricted privileges.  For Linux systems, this usually means the
>    root account
> 
> Composed (key:value) tags
> -------------------------
> 
> The more specific tags can be achieved by composing a predefined key
> with a value.  For instance, to tag a test as needing a specific
> CPU flag:
> 
>  * cpu_flag:vmx
> 
> Or a specific PCI device:
> 
>  * pci_id:8086:08b2
> 
> Or even a software package:
> 
>  * package:gcc
> 
> Or a package group altogether:
> 
>  * package_group:development-tools
> 
> Some examples
> -------------
> 
>  * ``cpu,x86_64`` - The test exercises the CPU and requires a
>    ``x86_64`` based platform
> 
>  * ``net,privileged,pci_id:14e4:1657`` - The test exercises either a
>    network device or the network stack, needs super user privileges
>    and a "Broadcom Limited NetXtreme BCM5719 Gigabit Ethernet PCIe
>    (rev 01)" device.

In my understanding, one of the key design aspects of tags is
that they're user-defined, optional, and totally arbitrary to the
rest of Avocado.  In other words, to Avocado there's no semantics
in a tag called "ppc64", "priviledged" or "pci_id:8086:08b2".

This should be clear in the documentation and in this RFC,
otherwise users might be tempted to start tagging tests following
some sort of "official list of tags" provided by Avocado, or
coding features that depend on some specific tag.

(or is this actually your intent?)

> 
> Looking at test tags
> ====================
> 
> Currently, there's no way to actually list the test tags from the
> command line, alongside the test name themselves.  An RFE for fixing
> this has been filed at https://trello.com/c/NXrbKEJC .

+1 to this.

> 
> Do users have to provide all the ``--filter-by-tags`` themselves?
> =================================================================
> 
> The test runner can certainly help here, getting system information
> when the job starts, and feeding them to the filtering.  This is yet
> another reason why coming up with a good set of guidelines for tagging
> tests is important.
> 
> In some ways, this can be seen similar to a dependency resolution
> mechanism for tests, only that at this point it will not resolve the
> requirements.  It will only filter out tests that can't (or shouldn't)
> be loaded on the current system.
> 
> Effectively, instead of many in-tests checks, and many SKIPs/CANCELs,
> the system information can be loaded once, and the only relevant tests
> will be part of the tests suite.
> 
> A list of the tests that were filtered out from the job test suite can
> certainly be a useful part of the job results.

This is close to what I had in mind years ago when I proposed a
simple dependency resolution mechanism, I think we discussed
it in the past:

 - Tests could have a set of tags listed as dependencies (I don't
   think generic tags should be used for it);
 - Environments where tests are run provide a list of tags as
   capabilities;
 - Avocado, when running tests, only runs the test in
   environments where all dependencies are matched by
   capabilities.

> 
> As in every RFC, feedback is extremely welcome!
> 

I think the generic tags mechanism should be kept arbitrary and
abstract. My first reaction is that there should be no
interpretation of the contents of the tags by other parts of the
system or "official list of tags and their semantics". And I'm
not sure if this is what you're proposing. :-)

Thanks.
   - Ademar

> 
> -- 
> Cleber Rosa
> [ Sr Software Engineer - Virtualization Team - Red Hat ]
> [ Avocado Test Framework - avocado-framework.github.io ]
> [  7ABB 96EB 8B46 B94D 5E0F  E9BB 657E 8D33 A5F2 09F3  ]
> 




-- 
Ademar Reis
Red Hat

^[:wq!