guides/contributing/unit_test.rst

.. SPDX-License-Identifier: BSD-3-Clause
   Copyright 2021 The DPDK contributors

DPDK Unit 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
<https://en.wikipedia.org/wiki/XUnit>`_.


Background
----------

The in-tree testing infrastructure for DPDK consists of
multiple applications and support tools.
The primary tools are the `dpdk-test` application,
and the ``meson test`` infrastructure.
These two are the primary ways through which
a user will interact with the DPDK testing infrastructure.

There exists a bit of confusion with the test suite and test case separation
with respect to `dpdk-test` and ``meson test``.
Both have a concept of test suite and test case.
In both, the concept is similar.
A test suite is a group of test cases,
and a test case represents the steps needed to test a particular set of code.
Where needed, they will be disambiguated by the word `Meson`
to denote a Meson test suite / case.


Running a test
--------------

DPDK tests are run via the main test runner, the `dpdk-test` app.
The `dpdk-test` app is a command-line interface that facilitates
running various tests or test suites.

There are three 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::

   $ ./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...
   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 --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...
   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', or a negative value).

The third form is an alternative
to providing the test suite name in an environment variable.
The unit test app can accept test suite names via command line arguments::

   $ ./build/app/test/dpdk-test --dpdk-options-here version_autotest version_autotest
   EAL: Detected 8 lcore(s)
   EAL: Detected 1 NUMA nodes
   EAL: Static memory layout is selected, amount of reserved memory can be...
   EAL: Detected static linkage of DPDK
   EAL: Multi-process socket /run/user/26934/dpdk/rte/mp_socket
   EAL: Selected IOVA mode 'VA'
   TELEMETRY: No legacy callbacks, legacy socket not created
   APP: HPET is not enabled, using TSC as default timer
   RTE>>version_autotest
   Version string: 'DPDK 21.08.0-rc0'
   Test OK
   RTE>>version_autotest
   Version string: 'DPDK 21.08.0-rc0'
   Test OK
   RTE>>

The primary benefit here is specifying multiple test names,
which is not possible with the ``DPDK_TEST`` environment variable.

Additionally, it is possible to specify additional test parameters
via the ``DPDK_TEST_PARAMS`` argument,
in case some tests need additional configuration.
This isn't currently used in the Meson test suites.


Running test cases via Meson
----------------------------

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 Meson test suites.
After building via ``ninja``, the ``meson test`` command
with no arguments will execute the Meson test suites.

There are five pre-configured Meson test suites.
The first 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 is the **perf** tests.
These test suites can take longer to run and do performance evaluations.
The third is the **driver** test suite,
which is mostly for special hardware related testing (such as `cryptodev`).
The fourth suite is the **debug** suite.
These tests mostly are used to dump system information.
The last suite is the **extra** suite for tests having some known issues.

The Meson test suites can be selected by adding the ``--suite`` option
to the ``meson test`` command.
Ex: ``meson test --suite fast-tests``::

   $ meson test -C build --suite fast-tests
   ninja: Entering directory `/home/aconole/git/dpdk/build'
   [2543/2543] Linking target app/test/dpdk-test.
   1/60 DPDK:fast-tests / acl_autotest          OK       3.17 s
   2/60 DPDK:fast-tests / bitops_autotest       OK       0.22 s
   3/60 DPDK:fast-tests / byteorder_autotest    OK       0.22 s
   4/60 DPDK:fast-tests / cmdline_autotest      OK       0.28 s
   5/60 DPDK:fast-tests / common_autotest       OK       0.57 s
   6/60 DPDK:fast-tests / cpuflags_autotest     OK       0.27 s
   ...

The ``meson test`` command can also execute individual Meson test cases
via the command line by adding the test names as an argument::

   $ meson test -C build version_autotest
   ninja: Entering directory `/home/aconole/git/dpdk/build'
   [2543/2543] Linking target app/test/dpdk-test.
   1/1 DPDK:fast-tests / version_autotest OK             0.17s
   ...

Note that these test cases must be known to Meson
for the ``meson test`` command to run them.
Simply adding a new test to the `dpdk-test` application isn't enough.
See the section `Adding a suite or test case to Meson`_ for more details.


Adding tests to dpdk-test application
-------------------------------------

Unit tests should be added to the system
whenever we introduce new functionality to DPDK,
as well as whenever a bug is resolved.
This helps the DPDK project to catch regressions as they are introduced.

The DPDK test application supports two layers of tests:
   #. *test cases* which are individual tests
   #. *test suites* which are groups of test cases

To add a new test suite 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 important functions for interacting with the test harness:

   ``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.

   ``unit_test_suite_runner(struct unit_test_suite *)``
      Returns a runner for a full test suite object,
      which contains a test suite name, setup, tear down,
      a pointer to a list of sub-testsuites,
      and vector of unit test cases.

Each test suite has a setup and tear down 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 tear down.

Each test suite may use a nested list of sub-testsuites,
which are iterated by the ``unit_test_suite_runner``.
This support allows for better granularity when designing test suites.
The sub-testsuites list can also be used in parallel with the vector of test cases,
in this case the test cases will be run,
and then each sub-testsuite is executed.
To see an example of a test suite using sub-testsuites,
see *app/test/test_cryptodev.c*.

Test cases are added to the ``.unit_test_cases`` element
of the appropriate unit test suite structure.
An example of both a test suite and a case:

.. 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.

Sub-testsuites can be added to the ``.unit_test_suites`` element
of the unit test suite structure, for example:

.. code-block:: c
   :linenos:

   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_parent_testsuite = {
          .suite_name = "EXAMPLE PARENT TEST SUITE",
          .setup = testsuite_setup,
          .teardown = testsuite_teardown,
          .unit_test_cases = {TEST_CASES_END()}
   };

   static int sub_testsuite_setup(void) { return TEST_SUCCESS; }
   static void sub_testsuite_teardown(void) { }

   static struct unit_test_suite example_sub_testsuite = {
          .suite_name = "EXAMPLE SUB TEST SUITE",
          .setup = sub_testsuite_setup,
          .teardown = sub_testsuite_teardown,
          .unit_test_cases = {
               TEST_CASE_ST(ut_setup, ut_teardown, test_case_first),

               TEST_CASES_END(), /**< NULL terminate unit test array */
          },
   };

   static struct unit_test_suite end_testsuite = {
          .suite_name = NULL,
          .setup = NULL,
          .teardown = NULL,
          .unit_test_suites = NULL
   };

   static int example_tests()
   {
       uint8_t ret, i = 0;
       struct unit_test_suite *sub_suites[] = {
              &example_sub_testsuite,
              &end_testsuite /**< NULL test suite to indicate end of list */
        };

       example_parent_testsuite.unit_test_suites =
               malloc(sizeof(struct unit_test_suite *) * RTE_DIM(sub_suites));

       for (i = 0; i < RTE_DIM(sub_suites); i++)
           example_parent_testsuite.unit_test_suites[i] = sub_suites[i];

       ret = unit_test_suite_runner(&example_parent_testsuite);
       free(example_parent_testsuite.unit_test_suites);

       return ret;
   }

   REGISTER_TEST_COMMAND(example_autotest, example_tests);


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 defined 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 available.
The 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.
Example::

   $ meson test -C build --suite fast-tests
   ninja: Entering directory `/home/aconole/git/dpdk/build
   [2543/2543] Linking target app/test/dpdk-test.
   1/60 DPDK:fast-tests / acl_autotest          OK       3.17 s
   2/60 DPDK:fast-tests / bitops_autotest       OK       0.22 s
   3/60 DPDK:fast-tests / byteorder_autotest    OK       0.22 s
   ...
   46/60 DPDK:fast-tests / ipsec_autotest       SKIP     0.22 s
   ...


Checking code coverage
----------------------

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 setup build -Db_coverage=true
   $ meson test -C build --suite fast-tests
   $ ninja coverage-html -C build

The above will generate an HTML report
in the `build/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 or test case to Meson
------------------------------------

Adding to one of the Meson test suites 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 will be run
as part of the appropriate class (fast, perf, driver, etc.).

A user or developer can confirm that a test is known to Meson
by using the ``--list`` option::

   $ meson test -C build --list
   DPDK:fast-tests / acl_autotest
   DPDK:fast-tests / bitops_autotest
   ...

Some of these test suites are run during continuous integration tests,
making regression checking automatic for new patches submitted to the project.

In general, when a test is added to the `dpdk-test` application,
it probably should be added to a Meson test suite,
but the choice is left to maintainers and individual developers.
Preference is to add tests to the Meson test suites.


Running cryptodev tests
-----------------------

When running cryptodev tests, the user must create any required virtual device
via EAL arguments, as this is not automatically done by the test::

   $ ./build/app/test/dpdk-test --vdev crypto_aesni_mb
   $ meson test -C build --suite driver-tests \
                --test-args="--vdev crypto_aesni_mb"

.. note::

   The ``cryptodev_scheduler_autotest`` is the only exception to this.
   This vdev will be created automatically by the test app,
   as it requires a more complex setup than other vdevs.