; Summary: add test dependencies
; Owner: Tim
; Reporter: Tim, AGL, Seimens
; Status: in progress
; Priority: very high

= Description =
Dependencies are important to avoid running tests that have problems.

This feature allows the test creator to specify a set of dependencies that
are checked before a test is invoked.  It is intended that this be used
for high-level sanity-checks - that is, to specify resources or configurations
that, if missing, invalidate the entire test.  If these are missing it
makes it impossible to run the test.

Some tests check for features themselves, and abort the test or skip sub-tests
if the features cannot be found.  Individual tests use their own mechanisms
for testing for these types of conditions.

These are checks intended to be used by the base script to validate whether
a particular test even applies to a certain target (or target configuration).

The dependency checks are processed during the pre_test phase, and if the dependencies are not met, the test is aborted with a failure.

== Existing support ==
Fuego already supports the following mechanisms for detecting dependencies:
 * [[function_check_capability|check_capability]] - check for the presence of a CAP_''FEATURE'' environment variable
   * this is used to check free-form variables (defined in the board or distro files)
 * [[function_assert_define|assert_define]] - check for the presence of an environment variable
   * this is used to check for test_spec variables
 * [[function_is_on_target|is_on_target]] - check for the presence of a file on the target system

== Types of dependencies ==
Here are different types of dependencies that may be present:
 * dependency on a specific hardware feature (such as touchpad, video, audio)
 * dependency on a system capability (such as networking, file system, user accounts, etc.)
 * dependency on a particular kernel configuration
   * these are often used as proxies for system capabilities or hardware
 * dependency on a file or executable on the target

== Outcomes ==
Should dependency failures result in test failures, or in some other
failure result - like "test skipped"?  Is this a particular type of failure
that should be reported differently from a regular test failure?

== Caching dependency information ==
It may save time to be able to cache the dependency information about 
a particular target board, if detecting the information is time-consuming.
For example, the 

== Industry survey ==
How to other systems allow for checking for test dependencies?
 * what does 0-day do for test dependencies?
   * uses 'need_xxx' directives (which are declarative)
   * the following are supported:
     * need_kconfig
       * examples:
          * need_kconfig: CONFIG_
     * need_x
     * need_kernel_headers
       * example: need_kernel_headers: true
     * need_memory
       * example: need_memory 2G
     * need_cpu
       * number of cpus, not used
 * what does fuego do? (imperative)
   * [[function_check_capability|check_capability]]
   * [[function_assert_define|assert_define]]
   * [[function_is_on_target|is_on_target]]
 * what does kernelci
 * what does LTP do?
   * 

= proposal =
 * declare dependencies as environment variables:
   * need_memory=2G
   * need_kconfig=CONFIG_MD_RAID ...
     * space-separated
   * need_env_vars=
   * need_kernel_headers=1

   



= Notes =
This was originally suggested in July of 2016 (probably in discussions at
LinuxCon Japan).


; backlink: [[Fuego Issues List]], [[Fuego To Do List]]