.. include:: replace.txt
.. highlight::  bash

Testing framework
-----------------

|ns3| consists of a simulation core engine, a set of models, example programs,
and tests.  Over time, new contributors contribute models, tests, and
examples.  A Python test program ``test.py`` serves as the test
execution manager; ``test.py`` can run test code and examples to
look for regressions, can output the results into a number of forms, and
can manage code coverage analysis tools.  On top of this, we layer
*buildslaves* that are automated build robots that perform
robustness testing by running the test framework on different systems
and with different configuration options.

Buildslaves
***********

At the highest level of |ns3| testing are the buildslaves (build robots).
If you are unfamiliar with
this system look at `<https://ns-buildmaster.ee.washington.edu:8010/>`_.
This is an open-source automated system that allows |ns3| to be rebuilt
and tested daily.  By running the buildbots on a number
of different systems we can ensure that |ns3| builds and executes
properly on all of its supported systems.

Users (and developers) typically will not interact with the buildslave system other
than to read its messages regarding test results.  If a failure is detected in
one of the automated build and test jobs, the buildbot will send an email to the
*ns-commits* mailing list.  This email will look something like

.. sourcecode::  text

  [Ns-commits] Build failed in Jenkins: daily-ubuntu-without-valgrind » Ubuntu-64-15.04 #926

  ...
  281 of 285 tests passed (281 passed, 3 skipped, 1 failed, 0 crashed, 0 valgrind errors)
  List of SKIPped tests:
    ns3-tcp-cwnd
    ns3-tcp-interoperability
    nsc-tcp-loss
  List of FAILed tests:
    random-variable-stream-generators
  + exit 1
  Build step 'Execute shell' marked build as failure

In the full details URL shown in the email, one can find links to the detailed test output.

The buildslave system will do its job quietly if there are no errors, and the
system will undergo build and test cycles every day to verify that all is well.

Test.py
*******
The buildbots use a Python program, ``test.py``, that is responsible for
running all of the tests and collecting the resulting reports into a human-
readable form.  This program is also available for use by users and developers
as well.

``test.py`` is very flexible in allowing the user to specify the number
and kind of tests to run; and also the amount and kind of output to generate.

Before running ``test.py``, make sure that ns3's examples and tests
have been built by doing the following

::

  $ ./waf configure --enable-examples --enable-tests
  $ ./waf build

By default, ``test.py`` will run all available tests and report status
back in a very concise form.  Running the command

::

  $ ./test.py

will result in a number of ``PASS``, ``FAIL``, ``CRASH`` or ``SKIP``
indications followed by the kind of test that was run and its display name.

.. sourcecode:: text

  Waf: Entering directory `/home/craigdo/repos/ns-3-allinone-test/ns-3-dev/build'
  Waf: Leaving directory `/home/craigdo/repos/ns-3-allinone-test/ns-3-dev/build'
  'build' finished successfully (0.939s)
  FAIL: TestSuite propagation-loss-model
  PASS: TestSuite object-name-service
  PASS: TestSuite pcap-file-object
  PASS: TestSuite ns3-tcp-cwnd
  ...
  PASS: TestSuite ns3-tcp-interoperability
  PASS: Example csma-broadcast
  PASS: Example csma-multicast

This mode is intended to be used by users who are interested in determining if
their distribution is working correctly, and by developers who are interested
in determining if changes they have made have caused any regressions.

There are a number of options available to control the behavior of ``test.py``.
if you run ``test.py --help`` you should see a command summary like:

.. sourcecode:: text

  Usage: test.py [options]

  Options:
    -h, --help            show this help message and exit
    -b BUILDPATH, --buildpath=BUILDPATH
                          specify the path where ns-3 was built (defaults to the
                          build directory for the current variant)
    -c KIND, --constrain=KIND
                          constrain the test-runner by kind of test
    -e EXAMPLE, --example=EXAMPLE
                          specify a single example to run (no relative path is
                          needed)
    -d, --duration        print the duration of each test suite and example
    -e EXAMPLE, --example=EXAMPLE
                          specify a single example to run (no relative path is
                          needed)
    -u, --update-data     If examples use reference data files, get them to re-
                          generate them
    -f FULLNESS, --fullness=FULLNESS
                          choose the duration of tests to run: QUICK, EXTENSIVE,
                          or TAKES_FOREVER, where EXTENSIVE includes QUICK and
                          TAKES_FOREVER includes QUICK and EXTENSIVE (only QUICK
                          tests are run by default)
    -g, --grind           run the test suites and examples using valgrind
    -k, --kinds           print the kinds of tests available
    -l, --list            print the list of known tests
    -m, --multiple        report multiple failures from test suites and test
                          cases
    -n, --nowaf           do not run waf before starting testing
    -p PYEXAMPLE, --pyexample=PYEXAMPLE
                          specify a single python example to run (with relative
                          path)
    -r, --retain          retain all temporary files (which are normally
                          deleted)
    -s TEST-SUITE, --suite=TEST-SUITE
                          specify a single test suite to run
    -t TEXT-FILE, --text=TEXT-FILE
                          write detailed test results into TEXT-FILE.txt
    -v, --verbose         print progress and informational messages
    -w HTML-FILE, --web=HTML-FILE, --html=HTML-FILE
                          write detailed test results into HTML-FILE.html
    -x XML-FILE, --xml=XML-FILE
                          write detailed test results into XML-FILE.xml

If one specifies an optional output style, one can generate detailed descriptions
of the tests and status.  Available styles are ``text`` and ``HTML``.
The buildbots will select the HTML option to generate HTML test reports for the
nightly builds using

::

  $ ./test.py --html=nightly.html

In this case, an HTML file named ''nightly.html'' would be created with a pretty
summary of the testing done.  A ''human readable'' format is available for users
interested in the details.

::

  $ ./test.py --text=results.txt

In the example above, the test suite checking the |ns3| wireless
device propagation loss models failed.  By default no further information is
provided.

To further explore the failure, ``test.py`` allows a single test suite
to be specified.  Running the command

::

  $ ./test.py --suite=propagation-loss-model

or equivalently

::

  $ ./test.py -s propagation-loss-model

results in that single test suite being run.

.. sourcecode:: text

  FAIL: TestSuite propagation-loss-model

To find detailed information regarding the failure, one must specify the kind
of output desired.  For example, most people will probably be interested in
a text file::

  $ ./test.py --suite=propagation-loss-model --text=results.txt

This will result in that single test suite being run with the test status written to
the file ''results.txt''.

You should find something similar to the following in that file

.. sourcecode:: text

  FAIL: Test Suite ''propagation-loss-model'' (real 0.02 user 0.01 system 0.00)
  PASS: Test Case "Check ... Friis ... model ..." (real 0.01 user 0.00 system 0.00)
  FAIL: Test Case "Check ... Log Distance ... model" (real 0.01 user 0.01 system 0.00)
    Details:
      Message:   Got unexpected SNR value
      Condition: [long description of what actually failed]
      Actual:    176.395
      Limit:     176.407 +- 0.0005
      File:      ../src/test/ns3wifi/propagation-loss-models-test-suite.cc
      Line:      360

Notice that the Test Suite is composed of two Test Cases.  The first test case
checked the Friis propagation loss model and passed.  The second test case
failed checking the Log Distance propagation model.  In this case, an SNR of
176.395 was found, and the test expected a value of 176.407 correct to three
decimal places.  The file which implemented the failing test is listed as well
as the line of code which triggered the failure.

If you desire, you could just as easily have written an HTML file using the
``--html`` option as described above.

Typically a user will run all tests at least once after downloading
|ns3| to ensure that his or her environment has been built correctly
and is generating correct results according to the test suites.  Developers
will typically run the test suites before and after making a change to ensure
that they have not introduced a regression with their changes.  In this case,
developers may not want to run all tests, but only a subset.  For example,
the developer might only want to run the unit tests periodically while making
changes to a repository.  In this case, ``test.py`` can be told to constrain
the types of tests being run to a particular class of tests.  The following
command will result in only the unit tests being run::

  $ ./test.py --constrain=unit

To see a quick list of the legal kinds of constraints, you can ask for them
to be listed.  The following command

::

  $ ./test.py --kinds

will result in the following list being displayed:

.. sourcecode:: text

  Waf: Entering directory `/home/craigdo/repos/ns-3-allinone-test/ns-3-dev/build'
  Waf: Leaving directory `/home/craigdo/repos/ns-3-allinone-test/ns-3-dev/build'
  'build' finished successfully (0.939s)Waf: Entering directory `/home/craigdo/repos/ns-3-allinone-test/ns-3-dev/build'
  core:        Run all TestSuite-based tests (exclude examples)
  example:     Examples (to see if example programs run successfully)
  performance: Performance Tests (check to see if the system is as fast as expected)
  system:      System Tests (spans modules to check integration of modules)
  unit:        Unit Tests (within modules to check basic functionality)

Any of these kinds of test can be provided as a constraint using the ``--constraint``
option.

To see a quick list of all of the test suites available, you can ask for them
to be listed.  The following command,

::

  $ ./test.py --list

will result in a list of the test suite being displayed, similar to

.. sourcecode:: text

  Waf: Entering directory `/home/craigdo/repos/ns-3-allinone-test/ns-3-dev/build'
  Waf: Leaving directory `/home/craigdo/repos/ns-3-allinone-test/ns-3-dev/build'
  'build' finished successfully (0.939s)

  Test Type    Test Name
  ---------    ---------
  performance  many-uniform-random-variables-one-get-value-call
  performance  one-uniform-random-variable-many-get-value-calls
  performance  type-id-perf
  system       buildings-pathloss-test
  system       buildings-shadowing-test
  system       devices-mesh-dot11s-regression
  system       devices-mesh-flame-regression
  system       epc-gtpu
  ...
  unit         wimax-phy-layer
  unit         wimax-service-flow
  unit         wimax-ss-mac-layer
  unit         wimax-tlv
  example      adhoc-aloha-ideal-phy
  example      adhoc-aloha-ideal-phy-matrix-propagation-loss-model
  example      adhoc-aloha-ideal-phy-with-microwave-oven
  example      aodv
  ...

Any of these listed suites can be selected to be run by itself using the
``--suite`` option as shown above.

To run multiple test suites at once it is possible to use a 'Unix filename pattern matching'
style, e.g.,

::

     $ ../test.py -s 'ipv6*'

Note the use of quotes. The result is similar to

.. sourcecode:: text

  PASS: TestSuite ipv6-protocol
  PASS: TestSuite ipv6-packet-info-tag
  PASS: TestSuite ipv6-list-routing
  PASS: TestSuite ipv6-extension-header
  PASS: TestSuite ipv6-address-generator
  PASS: TestSuite ipv6-raw
  PASS: TestSuite ipv6-dual-stack
  PASS: TestSuite ipv6-fragmentation
  PASS: TestSuite ipv6-address-helper
  PASS: TestSuite ipv6-address
  PASS: TestSuite ipv6-forwarding
  PASS: TestSuite ipv6-ripng

Similarly to test suites, one can run a single C++ example program
using the ``--example`` option.  Note that the relative path for the
example does not need to be included and that the executables built
for C++ examples do not have extensions.  Furthermore, the example
must be registered as an example to the test framework; it is not
sufficient to create an example and run it through test.py; it must
be added to the relevant ``examples-to-run.py`` file, explained below.
Entering

::

  $ ./test.py --example=udp-echo

results in that single example being run.

.. sourcecode:: text

  PASS: Example examples/udp/udp-echo

You can specify the directory where |ns3| was built using the
``--buildpath`` option as follows.

::

  $ ./test.py --buildpath=/home/craigdo/repos/ns-3-allinone-test/ns-3-dev/build/debug --example=wifi-simple-adhoc

One can run a single Python example program using the ``--pyexample``
option.  Note that the relative path for the example must be included
and that Python examples do need their extensions.  Entering

::

  $ ./test.py --pyexample=examples/tutorial/first.py

results in that single example being run.

.. sourcecode:: text

  PASS: Example examples/tutorial/first.py

Because Python examples are not built, you do not need to specify the
directory where |ns3| was built to run them.

Normally when example programs are executed, they write a large amount of trace
file data.  This is normally saved to the base directory of the distribution
(e.g., /home/user/ns-3-dev).  When ``test.py`` runs an example, it really
is completely unconcerned with the trace files.  It just wants to to determine
if the example can be built and run without error.  Since this is the case, the
trace files are written into a ``/tmp/unchecked-traces`` directory.  If you
run the above example, you should be able to find the associated
``udp-echo.tr`` and ``udp-echo-n-1.pcap`` files there.

The list of available examples is defined by the contents of the ''examples''
directory in the distribution.  If you select an example for execution using
the ``--example`` option, ``test.py`` will not make any attempt to decide
if the example has been configured or not, it will just try to run it and
report the result of the attempt.

When ``test.py`` runs, by default it will first ensure that the system has
been completely built.  This can be defeated by selecting the ``--nowaf``
option.

::

  $ ./test.py --list --nowaf

will result in a list of the currently built test suites being displayed, similar to:

.. sourcecode:: text

  propagation-loss-model
  ns3-tcp-cwnd
  ns3-tcp-interoperability
  pcap-file
  object-name-service
  random-variable-stream-generators

Note the absence of the ``Waf`` build messages.

``test.py`` also supports running the test suites and examples under valgrind.
Valgrind is a flexible program for debugging and profiling Linux executables.  By
default, valgrind runs a tool called memcheck, which performs a range of memory-
checking functions, including detecting accesses to uninitialised memory, misuse
of allocated memory (double frees, access after free, etc.) and detecting memory
leaks.  This can be selected by using the ``--grind`` option.

::

  $ ./test.py --grind

As it runs, ``test.py`` and the programs that it runs indirectly, generate large
numbers of temporary files.  Usually, the content of these files is not interesting,
however in some cases it can be useful (for debugging purposes) to view these files.
``test.py`` provides a ``--retain`` option which will cause these temporary
files to be kept after the run is completed.  The files are saved in a directory
named ``testpy-output`` under a subdirectory named according to the current Coordinated
Universal Time (also known as Greenwich Mean Time).

::

  $ ./test.py --retain

Finally, ``test.py`` provides a ``--verbose`` option which will print
large amounts of information about its progress.  It is not expected that this
will be terribly useful unless there is an error.  In this case, you can get
access to the standard output and standard error reported by running test suites
and examples.  Select verbose in the following way::

  $ ./test.py --verbose

All of these options can be mixed and matched.  For example, to run all of the
|ns3| core test suites under valgrind, in verbose mode, while generating an HTML
output file, one would do::

  $ ./test.py --verbose --grind --constrain=core --html=results.html

TestTaxonomy
************

As mentioned above, tests are grouped into a number of broadly defined
classifications to allow users to selectively run tests to address the different
kinds of testing that need to be done.

* Build Verification Tests
* Unit Tests
* System Tests
* Examples
* Performance Tests

Moreover, each test is further classified according to the expected time needed to
run it. Tests are classified as:

* QUICK
* EXTENSIVE
* TAKES_FOREVER

Note that specifying EXTENSIVE fullness will also run tests in QUICK category.
Specifying TAKES_FOREVER will run tests in EXTENSIVE and QUICK categories.
By default, only QUICK tests are ran.

As a rule of thumb, tests that must be run to ensure |ns3| coherence should be
QUICK (i.e., take a few seconds). Tests that could be skipped, but are nice to do
can be EXTENSIVE; these are tests that typically need minutes. TAKES_FOREVER is
left for tests that take a really long time, in the order of several minutes.
The main classification goal is to be able to run the buildbots in a reasonable
time, and still be able to perform more extensive tests when needed.

Unit Tests
++++++++++

Unit tests are more involved tests that go into detail to make sure that a
piece of code works as advertised in isolation.  There is really no reason
for this kind of test to be built into an |ns3| module.  It turns out, for
example, that the unit tests for the object name service are about the same
size as the object name service code itself.  Unit tests are tests that
check a single bit of functionality that are not built into the |ns3| code,
but live in the same directory as the code it tests.  It is possible that
these tests check integration of multiple implementation files in a module
as well.  The file src/core/test/names-test-suite.cc is an example of this kind
of test.  The file src/network/test/pcap-file-test-suite.cc is another example
that uses a known good pcap file as a test vector file.  This file is stored
locally in the src/network directory.

System Tests
++++++++++++

System tests are those that involve more than one module in the system.  We
have lots of this kind of test running in our current regression framework,
but they are typically overloaded examples.  We provide a new place
for this kind of test in the directory ``src/test``.  The file
src/test/ns3tcp/ns3-interop-test-suite.cc is an example of this kind of
test.  It uses NSC TCP to test the |ns3| TCP implementation.  Often there
will be test vectors required for this kind of test, and they are stored in
the directory where the test lives.  For example,
ns3tcp-interop-response-vectors.pcap is a file consisting of a number of TCP
headers that are used as the expected responses of the |ns3| TCP under test
to a stimulus generated by the NSC TCP which is used as a ''known good''
implementation.

Examples
++++++++

The examples are tested by the framework to make sure they built and
will run.  Limited checking is done on examples; currently the pcap
files are just written off into /tmp to be discarded.  If the example
runs (don't crash) and the exit status is zero, the example will pass
the smoke test.

Performance Tests
+++++++++++++++++

Performance tests are those which exercise a particular part of the system
and determine if the tests have executed to completion in a reasonable time.

Running Tests
*************

Tests are typically run using the high level ``test.py`` program. To get a list of the available command-line options, run ``test.py --help``

The test program ``test.py`` will run both tests and those examples that
have been added to the list to check.  The difference between tests
and examples is as follows.  Tests generally check that specific simulation
output or events conforms to expected behavior.  In contrast, the output
of examples is not checked, and the test program merely checks the exit
status of the example program to make sure that it runs without error.

Briefly, to run all tests, first one must configure tests during configuration
stage, and also (optionally) examples if examples are to be checked:

::

   $ ./waf --configure --enable-examples --enable-tests

Then, build |ns3|, and after it is built, just run ``test.py``.  ``test.py -h``
will show a number of configuration options that modify the behavior
of test.py.

The program ``test.py`` invokes, for C++ tests and examples, a lower-level
C++ program called ``test-runner`` to actually run the tests.  As discussed
below, this ``test-runner`` can be a helpful way to debug tests.

Debugging Tests
***************

The debugging of the test programs is best performed running the low-level
test-runner program. The test-runner is the bridge from generic Python
code to |ns3| code. It is written in C++ and uses the automatic test
discovery process in the |ns3| code to find and allow execution of all
of the various tests.

The main reason why ``test.py`` is not suitable for debugging is that it is
not allowed for logging to be turned on using the ``NS_LOG`` environmental
variable when test.py runs.  This limitation does not apply to the test-runner
executable. Hence, if you want to see logging output from your tests, you
have to run them using the test-runner directly.

In order to execute the test-runner, you run it like any other |ns3| executable
-- using ``waf``.  To get a list of available options, you can type::

  $ ./waf --run "test-runner --help"

You should see something like the following

.. sourcecode:: text

  Usage: /home/craigdo/repos/ns-3-allinone-test/ns-3-dev/build/utils/ns3-dev-test-runner-debug [OPTIONS]

  Options:
  --help                 : print these options
  --print-test-name-list : print the list of names of tests available
  --list                 : an alias for --print-test-name-list
  --print-test-types     : print the type of tests along with their names
  --print-test-type-list : print the list of types of tests available
  --print-temp-dir       : print name of temporary directory before running
                           the tests
  --test-type=TYPE       : process only tests of type TYPE
  --test-name=NAME       : process only test whose name matches NAME
  --suite=NAME           : an alias (here for compatibility reasons only)
                           for --test-name=NAME
  --assert-on-failure    : when a test fails, crash immediately (useful
                           when running under a debugger
  --stop-on-failure      : when a test fails, stop immediately
  --fullness=FULLNESS    : choose the duration of tests to run: QUICK,
                           EXTENSIVE, or TAKES_FOREVER, where EXTENSIVE
                           includes QUICK and TAKES_FOREVER includes
                           QUICK and EXTENSIVE (only QUICK tests are
                           run by default)
  --verbose              : print details of test execution
  --xml                  : format test run output as xml
  --tempdir=DIR          : set temp dir for tests to store output files
  --datadir=DIR          : set data dir for tests to read reference files
  --out=FILE             : send test result to FILE instead of standard output
  --append=FILE          : append test result to FILE instead of standard output


There are a number of things available to you which will be familiar to you if
you have looked at ``test.py``.  This should be expected since the test-
runner is just an interface between ``test.py`` and |ns3|.  You
may notice that example-related commands are missing here.  That is because
the examples are really not |ns3| tests.  ``test.py`` runs them
as if they were to present a unified testing environment, but they are really
completely different and not to be found here.

The first new option that appears here, but not in test.py is the ``--assert-on-failure``
option.  This option is useful when debugging a test case when running under a
debugger like ``gdb``.  When selected, this option tells the underlying
test case to cause a segmentation violation if an error is detected.  This has
the nice side-effect of causing program execution to stop (break into the
debugger) when an error is detected.  If you are using gdb, you could use this
option something like,

::

  $ ./waf shell
  $ cd build/utils
  $ gdb ns3-dev-test-runner-debug
  $ run --suite=global-value --assert-on-failure

If an error is then found in the global-value test suite, a segfault would be
generated and the (source level) debugger would stop at the ``NS_TEST_ASSERT_MSG``
that detected the error.

To run one of the tests directly from the test-runner
using ``waf``, you will need to specify the test suite to run.
So you could use the shell and do::

  $ ./waf --run "test-runner --suite=pcap-file"

|ns3| logging is available when you run it this way, such as:

  $ NS_LOG="Packet" ./waf --run "test-runner --suite=pcap-file"

Test output
+++++++++++

Many test suites need to write temporary files (such as pcap files)
in the process of running the tests.  The tests then need a temporary directory
to write to.  The Python test utility (test.py) will provide a temporary file
automatically, but if run stand-alone this temporary directory must be provided.
It can be annoying to continually have to provide
a ``--tempdir``, so the test runner will figure one out for you if you don't
provide one.  It first looks for environment variables named ``TMP`` and
``TEMP`` and uses those.  If neither ``TMP`` nor ``TEMP`` are defined
it picks ``/tmp``.  The code then tacks on an identifier indicating what
created the directory (ns-3) then the time (hh.mm.ss) followed by a large random
number.  The test runner creates a directory of that name to be used as the
temporary directory.  Temporary files then go into a directory that will be
named something like

::

  /tmp/ns-3.10.25.37.61537845

The time is provided as a hint so that you can relatively easily reconstruct
what directory was used if you need to go back and look at the files that were
placed in that directory.

Another class of output is test output like pcap traces that are generated
to compare to reference output.  The test program will typically delete
these after the test suites all run.  To disable the deletion of test
output, run ``test.py`` with the "retain" option:

::

   $ ./test.py -r

and test output can be found in the ``testpy-output/`` directory.

Reporting of test failures
++++++++++++++++++++++++++

When you run a test suite using the test-runner it will run the test
and report PASS or FAIL.
To run more quietly, you need to specify an output file to which the tests will write their status using the ``--out`` option.
Try,

::

  $ ./waf --run "test-runner --suite=pcap-file --out=myfile.txt"


Debugging test suite failures
+++++++++++++++++++++++++++++

To debug test crashes, such as

.. sourcecode:: text

  CRASH: TestSuite wifi-interference

You can access the underlying test-runner program via gdb as follows, and
then pass the "--basedir=`pwd`" argument to run (you can also pass other
arguments as needed, but basedir is the minimum needed)::

  $ ./waf --command-template="gdb %s" --run "test-runner"
  Waf: Entering directory `/home/tomh/hg/sep09/ns-3-allinone/ns-3-dev-678/build'
  Waf: Leaving directory `/home/tomh/hg/sep09/ns-3-allinone/ns-3-dev-678/build'
  'build' finished successfully (0.380s)
  GNU gdb 6.8-debian
  Copyright (C) 2008 Free Software Foundation, Inc.
  L cense GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
  This is free software: you are free to change and redistribute it.
  There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
  and "show warranty" for details.
  This GDB was configured as "x86_64-linux-gnu"...
  (gdb) r --suite=
  Starting program: <..>/build/utils/ns3-dev-test-runner-debug --suite=wifi-interference
  [Thread debugging using libthread_db enabled]
  assert failed. file=../src/core/model/type-id.cc, line=138, cond="uid <= m_information.size () && uid != 0"
  ...

Here is another example of how to use valgrind to debug a memory problem
such as::

  VALGR: TestSuite devices-mesh-dot11s-regression

  $ ./waf --command-template="valgrind %s --suite=devices-mesh-dot11s-regression" --run test-runner

Class TestRunner
****************

The executables that run dedicated test programs use a TestRunner class.  This
class provides for automatic test registration and listing, as well as a way to
execute the individual tests.  Individual test suites use C++ global
constructors
to add themselves to a collection of test suites managed by the test runner.
The test runner is used to list all of the available tests and to select a test
to be run.  This is a quite simple class that provides three static methods to
provide or Adding and Getting test suites to a collection of tests.  See the
doxygen for class ``ns3::TestRunner`` for details.

Test Suite
**********

All |ns3| tests are classified into Test Suites and Test Cases.  A
test suite is a collection of test cases that completely exercise a given kind
of functionality.  As described above, test suites can be classified as,

* Build Verification Tests
* Unit Tests
* System Tests
* Examples
* Performance Tests

This classification is exported from the TestSuite class.  This class is quite
simple, existing only as a place to export this type and to accumulate test
cases.  From a user perspective, in order to create a new TestSuite in the
system one only has to define a new class that inherits from class ``TestSuite``
and perform these two duties.

The following code will define a new class that can be run by ``test.py``
as a ''unit'' test with the display name, ``my-test-suite-name``.

.. sourcecode:: cpp

  class MySuite : public TestSuite
  {
  public:
    MyTestSuite ();
  };

  MyTestSuite::MyTestSuite ()
    : TestSuite ("my-test-suite-name", UNIT)
  {
    AddTestCase (new MyTestCase, TestCase::QUICK);
  }

  static MyTestSuite myTestSuite;

The base class takes care of all of the registration and reporting required to
be a good citizen in the test framework.

Avoid putting initialization logic into the test suite or test case
constructors.  This is
because an instance of the test suite is created at run time
(due to the static variable above) regardless of whether the test is being
run or not.  Instead, the TestCase provides a virtual ``DoSetup`` method
that can be specialized to perform setup before ``DoRun`` is called.

Test Case
*********

Individual tests are created using a TestCase class.  Common models for the use
of a test case include "one test case per feature", and "one test case per method."
Mixtures of these models may be used.

In order to create a new test case in the system, all one has to do is to inherit
from the  ``TestCase`` base class, override the constructor to give the test
case a name and override the ``DoRun`` method to run the test.  Optionally,
override also the ``DoSetup`` method.

.. sourcecode:: cpp

  class MyTestCase : public TestCase
  {
    MyTestCase ();
    virtual void DoSetup (void);
    virtual void DoRun (void);
  };

  MyTestCase::MyTestCase ()
    : TestCase ("Check some bit of functionality")
  {
  }

  void
  MyTestCase::DoRun (void)
  {
    NS_TEST_ASSERT_MSG_EQ (true, true, "Some failure message");
  }

Utilities
*********

There are a number of utilities of various kinds that are also part of the
testing framework.  Examples include a generalized pcap file useful for
storing test vectors; a generic container useful for transient storage of
test vectors during test execution; and tools for generating presentations
based on validation and verification testing results.

These utilities are not documented here, but for example, please see
how the TCP tests found in ``src/test/ns3tcp/`` use pcap files and reference
output.
