[dpdk-dev] [PATCH] guides: add a testing guide for developing tests

[Aaron Conole]

"Kinsella, Ray" <mdr at ashroe.eu> writes:

> On 08/02/2021 16:52, Aaron Conole wrote:
>> The DPDK testing infrastructure includes a comprehensive set of
>> libraries, utilities, and CI integrations for developers to test
>> their code changes.  This isn't well documented, however.
>> 
>> Document the basics for adding a test suite to the infrastructure
>> and enabling that test suite for continuous integration platforms
>> so that newer developers can understand how to develop test suites
>> and test cases.
>> 
>> Signed-off-by: Aaron Conole <aconole at redhat.com>
>> ---
>> v0: Added information for TEST_SKIPPED and details about generating
>>     code coverage to help with ideas for writing unit test cases.
>> 
>>  doc/guides/contributing/index.rst   |   1 +
>>  doc/guides/contributing/testing.rst | 231 ++++++++++++++++++++++++++++
>>  2 files changed, 232 insertions(+)
>>  create mode 100644 doc/guides/contributing/testing.rst
>> 
>> diff --git a/doc/guides/contributing/index.rst b/doc/guides/contributing/index.rst
>> index 2fefd91931..41909d949b 100644
>> --- a/doc/guides/contributing/index.rst
>> +++ b/doc/guides/contributing/index.rst
>> @@ -14,6 +14,7 @@ Contributor's Guidelines
>>      abi_versioning
>>      documentation
>>      patches
>> +    testing
>>      vulnerability
>>      stable
>>      cheatsheet
>> diff --git a/doc/guides/contributing/testing.rst b/doc/guides/contributing/testing.rst
>> new file mode 100644
>> index 0000000000..3ade654772
>> --- /dev/null
>> +++ b/doc/guides/contributing/testing.rst
>> @@ -0,0 +1,231 @@
>> +..  SPDX-License-Identifier: BSD-3-Clause
>> +    Copyright 2018 The DPDK contributors
>> +
>> +.. _testing_guidelines:
>> +
>> +DPDK Testing Guidelines
>> +=======================
>> +
>> +This document outlines the guidelines for running and adding new
>> +tests to the in-tree DPDK test suites.
>> +
>> +The DPDK test suite model is loosely based on the xunit model, where
>> +tests are grouped into test suites, and suites are run by runners.
>> +For a basic overview, see the basic Wikipedia article on xunit:
>> +`xUnit - Wikipedia <https://en.wikipedia.org/wiki/XUnit>`_.
>> +
>> +
>> +Running a test
>> +--------------
>> +
>> +DPDK tests are run via the main test runniner, the `dpdk-test` app.
>
> runner

D'oh!

>> +The `dpdk-test` app is a command-line interface that facilitates
>> +running various tests or test suites.
>> +
>> +There are two modes of operation.  The first mode is as an interactive
>> +command shell that allows launching specific test suites.  This is
>> +the default operating mode of `dpdk-test` and can be done by::
>
> is the double :: intentional?

Yes - it designates the next block as a code block.

>> +
>> +  $ ./build/app/test/dpdk-test --dpdk-options-here
>> +  EAL: Detected 4 lcore(s)
>> +  EAL: Detected 1 NUMA nodes
>> + EAL: Static memory layout is selected, amount of reserved memory
>> can be adjusted with -m or --socket-mem
>> +  EAL: Multi-process socket /run/user/26934/dpdk/rte/mp_socket
>> +  EAL: Selected IOVA mode 'VA'
>> +  EAL: Probing VFIO support...
>> +  EAL: PCI device 0000:00:1f.6 on NUMA socket -1
>> +  EAL:   Invalid NUMA socket, default to 0
>> +  EAL:   probe driver: 8086:15d7 net_e1000_em
>> +  APP: HPET is not enabled, using TSC as default timer
>> +  RTE>>
>> +
>> +At the prompt, simply type the name of the test suite you wish to run
>> +and it will execute.
>> +
>> +The second form is useful for a scripting environment, and is used by
>> +the DPDK meson build system.  This mode is invoked by assigning a
>> +specific test suite name to the environment variable `DPDK_TEST`
>> +before invoking the `dpdk-test` command, such as::
>> +
>> +  $ DPDK_TEST=version_autotest ./build/app/test/dpdk-test --no-huge
>
> better to say --dpdk-options-here instead of --no-huge, as above. 

Okay, I can do that.

>> +  EAL: Detected 4 lcore(s)
>> +  EAL: Detected 1 NUMA nodes
>> + EAL: Static memory layout is selected, amount of reserved memory
>> can be adjusted with -m or --socket-mem
>> +  EAL: Multi-process socket /run/user/26934/dpdk/rte/mp_socket
>> +  EAL: Selected IOVA mode 'VA'
>> +  EAL: Probing VFIO support...
>> +  EAL: PCI device 0000:00:1f.6 on NUMA socket -1
>> +  EAL:   Invalid NUMA socket, default to 0
>> +  EAL:   probe driver: 8086:15d7 net_e1000_em
>> +  APP: HPET is not enabled, using TSC as default timer
>> +  RTE>>version_autotest
>> +  Version string: 'DPDK 20.02.0-rc0'
>> +  Test OK
>> +  RTE>>$
>> +
>> +The above shows running a specific test case.  On success, the return
>> +code will be '0', otherwise it will be set to some error value (such
>> +as '255').
>> +
>> +
>> +Running all tests
>> +-----------------
>> +
>> +In order to allow developers to quickly execute all the standard
>> +internal tests without needing to remember or look up each test suite
>> +name, the build system includes a standard way of executing the
>> +default test suites.  After building via `ninja`, the ``meson test``
>> +command will execute the standard tests and report errors.
>> +
>> +There are four groups of default test suites.  The first group is
>> +the **fast** test suite, which is the largest group of test cases.
>> +These are the bulk of the unit tests to validate functional blocks.
>> +The second group is the **perf** tests.  These test suites can take
>> +longer to run and do performance evaluations.  The third group is
>> +the **driver** test suite, which is mostly for special hardware
>> +related testing (such as `cryptodev`).  The last group are the
>> +**debug** tests.  These mostly are used to dump system information.
>> +
>> +The suites can be selected by adding the ``--suite`` option to the
>> +``meson test`` command.  Ex: ``meson test --suite fast-tests``
>
> show some console output in this section?

Okay.

>> +
>> +
>> +Adding test suites
>> +------------------
>> +
>> +To add a testsuite to the DPDK test application, create a new test
>> +file for that suite (ex: see *app/test/test_version.c* for the
>> +``version_autotest`` test suite).  There are two useful things:
>
> There are two useful things?

Okay, I will rephrase because it sounds awkward.  But I don't think it's
wrong ;)

>> +
>> +  1. REGISTER_TEST_COMMAND(command_name, function_to_execute)
>> +     Registers a test command with the name `command_name` and which
>> +     runs the function `function_to_execute` when `command_name` is
>> +     invoked.
>> +
>> +  2. unit_test_suite_runner(struct unit_test_suite \*)
>> +     Returns a runner for a full test suite object, which contains
>> +     a test suite name, setup, teardown, and vector of unit test
>> +     cases.
>> +
>> +Each test suite has a setup and teardown function that runs at the
>> +beginning and end of the test suite execution.  Each unit test has
>> +a similar function for test case setup and teardown.
>> +
>> +Adding test cases is controlled via the `.unit_test_cases` element
>
> Test cases are added to the .unit_test_cases element of the 
> of the unit test suite structure. 

Will rephrase.

>> +of the unit test suite.  Ex:
>> +
>> +.. code-block:: c
>> +   :linenos:
>> +
>> +   #include <time.h>
>> +
>> +   #include <rte_common.h>
>> +   #include <rte_cycles.h>
>> +   #include <rte_hexdump.h>
>> +   #include <rte_random.h>
>> +
>> +   #include "test.h"
>> +
>> +   static int testsuite_setup(void) { return TEST_SUCCESS; }
>> +   static void testsuite_teardown(void) { }
>> +
>> +   static int ut_setup(void) { return TEST_SUCCESS; }
>> +   static void ut_teardown(void) { }
>> +
>> +   static int test_case_first(void) { return TEST_SUCCESS; }
>> +
>> +   static struct unit_test_suite example_testsuite = {
>> +          .suite_name = "EXAMPLE TEST SUITE",
>> +          .setup = testsuite_setup,
>> +          .teardown = testsuite_teardown,
>> +          .unit_test_cases = {
>> +               TEST_CASE_ST(ut_setup, ut_teardown, test_case_first),
>> +
>> +               TEST_CASES_END(), /**< NULL terminate unit test array */
>> +          },
>> +   };
>> +
>> +   static int example_tests()
>> +   {
>> +       return unit_test_suite_runner(&example_testsuite);
>> +   }
>> +
>> +   REGISTER_TEST_COMMAND(example_autotest, example_tests);
>> +
>> +The above code block is a small example that can be used to create a
>> +complete test suite with test case.
>> +
>> +
>> +Designing a test
>> +----------------
>> +
>> +Test cases have multiple ways of indicating an error has occurred,
>> +in order to reflect failure state back to the runner.  Using the
>> +various methods of indicating errors can assist in not only validating
>> +the requisite functionality is working, but also to help debug when
>> +a change in environment or code has caused things to go wrong.
>> +
>> +The first way to indicate a generic error is by returning a test
>> +result failure, using the *TEST_FAILED* error code.  This is the most
>> +basic way of indicating that an error has occurred in a test routine.
>> +It isn't very informative to the user, so it should really be used in
>> +cases where the test has catastrophically failed.
>> +
>> +The preferred method of indicating an error is via the
>> +`RTE_TEST_ASSERT` family of macros, which will immediately return
>> +*TEST_FAILED* error condition, but will also log details about the
>> +failure.  The basic form is:
>> +
>> +.. code-block:: c
>> +
>> +   RTE_TEST_ASSERT(cond, msg, ...)
>> +
>> +In the above macro, *cond* is the condition to evaluate to **true**.
>> +Any generic condition can go here.  The *msg* parameter will be a
>> +message to display if *cond* evaluates to **false**.  Some specialized
>> +macros already exist.  See `lib/librte_eal/include/rte_test.h` for
>> +a list of pre-build test assertions.
>> +
>> +Sometimes it is important to indicate that a test needs to be
>> +skipped, either because the environment isn't able to support running
>> +the test, or because some requisite functionality isn't availble.  The
>
> available

D'oh!

>> +test suite supports returning a result of `TEST_SKIPPED` during test
>> +case setup, or during test case execution to indicate that the
>> +preconditions of the test aren't available.  A skipped test isn't the
>> +same as a failed test.  Failed tests indicate that all required
>> +functionality was enabled, and the environment was correct but the
>> +test failed due to some error in logic.  A skipped test indicates
>> +that the test setup wasn't available to run.
>
> Simpler to provide an example of a skipped test, than a long explanation?

I can do both.

>> +
>> +
>> +Checking code coverage
>> +----------------------
>> +One of the best ways to help design a test case is to add a new test
>> +which exercises functionality that doesn't currently have a test case.
>> +The best way to find these is to run the test suite with some
>> +additional code coverage reporting turned on.  
>
> I would drop the previous sentences.
> They would just confuse a reader looking to generate code coverage.

Okay.  I felt it was a bit strange to introduce code coverage here, and
I thought it was a needed bridge.  I can drop it.

>> The meson build system
>> +supports generating a code coverage report via the `-Db_coverage=true`
>> +option, in conjunction with a package like **lcov**, to generate an
>> +HTML code coverage report.  Example::
>> +
>> +  $ meson covered -Db_coverage=true
>> +  $ meson test -C covered --suite fast-tests
>> +  $ ninja coverage-html -C covered
>> +
>> +The above will generate an html report in the
>> +`covered/meson-logs/coveragereport/` directory that can be explored
>> +for detailed code covered information.  This can be used to assist
>> +in test development.
>> +
>> +
>> +Adding a suite to the default
>> +-----------------------------
>> +
>> +Adding to one of the default tests involves editing the appropriate
>> +meson build file `app/test/meson.build` and adding the command to
>> +the correct test suite class.  Once added, the new test suite will
>> +be run as part of the appropriate class (fast, perf, driver, etc.).
>> +
>> +Some of these default test suites are run during continuous integration
>> +tests, making regression checking automatic for new patches submitted
>> +to the project.
>>