[Avocado-devel] RFC: Guidelines for categorizing tests

[Cleber Rosa]

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.

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 .

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.

As in every RFC, feedback is extremely welcome!


-- 
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  ]

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