..	-*- mode: rst-mode -*-
..
.. Version number is filled in automatically.

.. |version| replace:: 1.2-15

==================================================
BTest - A Generic Driver for Powerful System Tests
==================================================

BTest is a powerful framework for writing system tests. Freely
borrowing some ideas from other packages, its main objective is to
provide an easy-to-use, straightforward driver for a suite of
shell-based tests. Each test consists of a set of command lines that
will be executed, and success is determined based on their exit
codes. ``btest`` comes with some additional tools that can be used
within such tests to robustly compare output against a previously established
baseline.

This document describes BTest |version|. See the ``CHANGES``
file in the source tree for version history.

.. contents::

Prerequisites
=============

BTest has the following prerequisites:

- Python version >= 3.9 (older versions may work, but are not well-tested).

- Bash. Note that on FreeBSD and Alpine Linux, bash is not installed by
  default. This is also required on Windows, in the form of Git's msys2, Cygwin,
  etc.

BTest has the following optional prerequisites to enable additional
functionality:

- Sphinx. Sphinx functionality is currently disabled on Windows.

- perf (Linux only).  Note that on Debian/Ubuntu, you also need to install
  the "linux-tools" package.

Windows Caveats
---------------

When running BTest on Windows, you must have a bash shell installed of some
sort. This can be from WSL, Cygwin, msys2, Git, or any number of other methods,
but ``bash.exe`` must be available. BTest will check for its existence at
startup and exit if it is not available.

A minor change must be made to any configuration value that is a path list. For
example, if you are setting the ``PATH`` environment variable from your
btest.cfg. In these cases, you should use ``$(pathsep)s`` in the configuration
instead of bare ``:`` or ``;`` values to separate the paths. This ensures that
both POSIX and Windows systems handle the path lists correctly.

Download and Installation
=========================

Installation is simple and standard via ``pip``::

    > pip install btest

Alternatively, you can download a tarball `from PyPI <https://pypi.org/project/btest/#files>`_
and install locally::

    > tar xzvf btest-*.tar.gz
    > cd btest-*
    > python3 setup.py install

The same approach also works on a local git clone of the source tree,
located at https://github.com/zeek/btest.

Each will install a few scripts: ``btest`` is the main driver program,
and there are a number of further helper scripts that we discuss below
(including ``btest-diff``, which is a tool for comparing output to a
previously established baseline).

.. _running btest:

Running BTest
=============

A BTest testsuite consists of one or more "btests", executed by the
``btest`` driver. Btests are plain text files in which ``btest``
identifies keywords with corresponding arguments that tell it what to
do. BTest is *not* a language; it recognizes keywords in any text
file, including when embedded in other scripting languages. A common
idiom in BTest is to use keywords to process the btest file via a
particular command, often a script interpreter. This approach feels
unusal at first, but lends BTest much of its flexibility: btest
files can contain pretty much anything, as long as ``btest``
identifies keywords in it.

``btest`` requires a `configuration file`_. With it, you can run
``btest`` on an existing testsuite in several ways:

- Point it at directories containing btests::

    > btest ./testsuite/

- Use the config file to enumerate directories to scan for tests,
  via the ``TestDirs`` `option`_::

    > btest

- Run btests selectively, by pointing ``btest`` at a specific test file::

    > btest ./testsuite/my.test

  More detail on this when we cover `test selection`_.

Writing a Test
==============

First Steps
-----------

In the most simple case, ``btest`` simply executes a set of command
lines, each of which must be prefixed with the ``@TEST-EXEC:``
keyword::

    > cat examples/t1
    @TEST-EXEC: echo "Foo" | grep -q Foo
    @TEST-EXEC: test -d .
    > btest examples/t1
    examples.t1 ... ok

The test passes as both command lines return success. If one of them
didn't, that would be reported::

    > cat examples/t2
    @TEST-EXEC: echo "Foo" | grep -q Foo
    @TEST-EXEC: test -d DOESNOTEXIST
    > btest examples/t2
    examples.t2 ... failed

Usually you will just run all tests found in a directory::

    > btest examples
    examples.t1 ... ok
    examples.t2 ... failed
    1 test failed

The file containing the test can simultaneously act as *its input*. Let's
say we want to verify a shell script::

    > cat examples/t3.sh
    # @TEST-EXEC: sh %INPUT
    ls /etc | grep -q passwd
    > btest examples/t3.sh
    examples.t3 ... ok

Here, ``btest`` executes (something similar to) ``sh
examples/t3.sh``, and then checks the return value as usual. The
example also shows that the ``@TEST-EXEC`` keyword can appear
anywhere, in particular inside the comment section of another
language.

Using Baselines
---------------

Now, let's say we want to verify the output of a program, making sure
that it matches our expectations---a common use case for BTest. To do
this, we rely on BTest's built-in support for test baselines. These
baselines record prior output of a test, adding support for
abstracting away brittle details such as ever-changing timestamps or
home directories. BTest comes with tooling to establish, update, and
verify baselines, and to plug in "`canonifiers`_": scripts that
abstract, or "normalize", troublesome detail from a baseline.

In our test, we first add a command line that produces the output we
want to check, and then run ``btest-diff`` to make sure it matches the
previously recorded baseline. ``btest-diff`` is itself just a script
that returns success if the output matches a pre-recorded baseline
after applying any required normalizations.

In the following example, we use an awk script as a fancy way to print all
file names starting with a dot in the user's home directory. We
write that list into a file called ``dots`` and then check whether
its content matches what we know from last time::

    > cat examples/t4.awk
    # @TEST-EXEC: ls -a $HOME | awk -f %INPUT >dots
    # @TEST-EXEC: btest-diff dots
    /^\.+/ { print $1 }

Note that each test gets its own little sandbox directory when run,
so by creating a file like ``dots``, you aren't cluttering up
anything.

The first time we run this test, we need to record a baseline. The
``btest`` command includes a baseline-update mode, set via ``-U``,
that achieves this::

    > btest -U examples/t4.awk

``btest-diff`` recognizes this update mode via an environment variable
set by ``btest``, and records the ``dots`` file in a separate baseline
folder. With this baseline in place, modifications to the output now
trigger a test failure::

    > btest examples/t4.awk
    examples.t4 ... ok
    > touch ~/.NEWDOTFILE
    > btest examples/t4.awk
    examples.t4 ... failed
    1 test failed

If we want to see what exactly changed in ``dots`` to trigger the
failure, ``btest`` allows us to record the discrepancies via a
*diagnostics* mode that records them in a file called ``.diag``::

    > btest -d examples/t4.awk
    examples.t4 ... failed
    % 'btest-diff dots' failed unexpectedly (exit code 1)
    % cat .diag
    == File ===============================
    [... current dots file ...]
    == Diff ===============================
    --- /Users/robin/work/binpacpp/btest/Baseline/examples.t4/dots
    2010-10-28 20:11:11.000000000 -0700
    +++ dots      2010-10-28 20:12:30.000000000 -0700
    @@ -4,6 +4,7 @@
    .CFUserTextEncoding
    .DS_Store
    .MacOSX
    +.NEWDOTFILE
    .Rhistory
    .Trash
    .Xauthority
    =======================================

    % cat .stderr
    [... if any of the commands had printed something to stderr, that would follow here ...]

Once we delete the new file, the test passes again::

    > rm ~/.NEWDOTFILE
    > btest -d examples/t4.awk
    examples.t4 ... ok

That's the essence of the functionality the ``btest`` package
provides. This example did not use canonifiers. We cover these,
and a number of additional options that extend or modify this basic
approach, in the following sections.

Reference
=========

Command Line Usage
------------------

``btest`` must be started with a list of tests and/or directories
given on the command line. In the latter case, the default is to
recursively scan the directories and assume all files found to be
tests to perform. It is however possible to exclude specific files and
directories by specifying a suitable `configuration file`_.

``btest`` returns exit code 0 if all tests have successfully passed,
and 1 otherwise. Exit code 1 can also result in case of other errors.

``btest`` accepts the following options:

-a ALTERNATIVE, --alternative=ALTERNATIVE
    Activates an alternative_ configuration defined in the
    configuration file. Multiple alternatives can be given as a
    comma-separated list (in this case, all specified tests are run
    once for each specified alternative). The alternatives ``-``
    and ``default`` refer to the standard setup, allowing tests to
    run with combinations of the latter and select alternatives.
    If an alternative is not defined in the configuration, ``btest``
    fails with exit code 1 and an according error message on stderr.

-A, --show-all
    Shows an output line for all tests that were run (this includes tests
    that passed, failed, or were skipped), rather than only failed tests.
    Note that this option has no effect when stdout is not a TTY
    (because all tests are shown in that case).

-b, --brief
    Does not output *anything* for tests which pass. If all tests
    pass, there will not be any output at all except final summary
    information.

-c CONFIG, --config=CONFIG
    Specifies an alternative `configuration file`_ to use. If not
    specified, the default is to use a file called ``btest.cfg``
    if found in the current directory. An alternative way to specify
    a different config file is with the ``BTEST_CFG`` environment
    variable (however, the command-line option overrides ``BTEST_CFG``).

-d, --diagnostics
    Reports diagnostics for all failed tests. The diagnostics
    include the command line that failed, its output to standard
    error, and potential additional information recorded by the
    command line for diagnostic purposes (see `@TEST-EXEC`_
    below). In the case of ``btest-diff``, the latter is the
    ``diff`` between baseline and actual output.

-D, --diagnostics-all
    Reports diagnostics for all tests, including those which pass.

-f DIAGFILE, --file-diagnostics=DIAGFILE
    Writes diagnostics for all failed tests into the given file.
    If the file already exists, it will be overwritten.

-g GROUPS, --groups=GROUPS
    Runs only tests assigned to the given test groups, see
    `@TEST-GROUP`_. Multiple groups can be given as a
    comma-separated list. Specifying groups with a leading ``-``
    leads to all tests to run that are *not* not part of them.
    Specifying a sole ``-`` as a group name selects all tests that
    do not belong to any group. (Note that if you combine these
    variants to create ambiguous situations, it's left
    undefined which tests will end up running).

-j THREADS, --jobs=THREADS
    Runs up to the given number of tests in parallel. If no number
    is given, BTest substitutes the number of available CPU cores
    as reported by the OS.

    By default, BTest assumes that all tests can be executed
    concurrently without further constraints. One can however
    ensure serialization of subsets by assigning them to the same
    serialization set, see `@TEST-SERIALIZE`_.

-q, --quiet
    Suppress information output other than about failed tests.
    If all tests pass, there will not be any output at all.

-r, --rerun
    Runs only tests that failed last time. After each execution
    (except when updating baselines), BTest generates a state file
    that records the tests that have failed. Using this option on
    the next run then reads that file back in and limits execution
    to those tests found in there.

-R FORMAT, --documentation=FORMAT
    Generates a reference of all tests and prints that to standard
    output. The output can be of two types, specified by
    ``FORMAT``: ``rst`` prints reStructuredText, and ``md`` prints
    Markdown. In the output each test includes the documentation
    string that's defined for it through ``@TEST-DOC``.

-s <kv>, --set=<kv>
    Takes a ``key=value`` argument and uses it to override a value
    used during parsing of the configuration file read by btest at
    startup. This can be used to override various default values
    prior to parsing. Can be passed multiple times to override
    different keys. See `defaults`_ for an example.

-t, --tmp-keep
    Does not delete any temporary files created for running the
    tests (including their outputs). By default, the temporary
    files for a test will be located in ``.tmp/<test>/``, where
    ``<test>`` is the relative path of the test file with all slashes
    replaced with dots and the file extension removed (e.g., the files
    for ``example/t3.sh`` will be in ``.tmp/example.t3``).

-T, --update-times
    Record new `timing`_ baselines for the current host for tests that
    have `@TEST-MEASURE-TIME`_. Tests are run as normal except that
    the timing measurements are recorded as the new baseline instead
    of being compared to a previous baseline.

--trace-file=TRACEFILE
    Record test execution timings in Chrome tracing format to the given
    file. If the file exists already, it is overwritten. The file can be
    loaded in Chrome-based browsers at `<about:tracing>`_, or converted to
    standalone HTML with `trace2html <https://pypi.org/project/trace2html/>`_.

-U, --update-baseline
    Records a new baseline for all ``btest-diff`` commands found
    in any of the specified tests. To do this, all tests are run
    as normal except that when ``btest-diff`` is executed, it
    does not compute a diff but instead considers the given file
    to be authoritative and records it as the version to compare
    with in future runs.

-u, --update-interactive
    Each time a ``btest-diff`` command fails in any tests that are
    run, ``btest`` will stop and ask whether or not the user wants to
    record a new baseline.

-v, --verbose
    Shows all test command lines as they are executed.

-w, --wait
    Interactively waits for ``<enter>`` after showing diagnostics
    for a test.

-x FILE, --xml=FILE
    Records test results in JUnit XML format to the given file.
    If the file exists already, it is overwritten.

-z RETRIES, --retries=RETRIES
    Retry any failed tests up to this many times to determine if
    they are unstable.

-i FILE, --tests-file=FILE
    Loads the list of tests to execute from a file. Each line in the
    file is interpreted as the name of a test, or a group of tests, to
    execute, just like the tests would be specified on the command
    line. Empty lines and lines starting with ``#`` are ignored. (This
    format is compatible with that of the ``btest`` `StateFile
    <state_file_>`_.)

.. _configuration file: configuration_
.. _configuration:

Configuration
-------------

Specifics of ``btest``'s execution can be tuned with a configuration
file, which by default is ``btest.cfg`` if that's found in the current
directory or parent directories. It can alternatively be specified
with the ``--config`` command line option (which will not search
parent directories), or a ``BTEST_CFG`` environment variable.
The configuration file is
"INI-style", and an example comes with the distribution, see
``btest.cfg.example``. A configuration file has one main section,
``btest``, that defines most options; as well as an optional section
for defining `environment variables`_ and further optional sections
for defining alternatives_.

Note that all paths specified in the configuration file are relative
to ``btest``'s *base directory*. The base directory is either the
one where the configuration file is located if such is given/found,
or the current working directory if not. One can also override it
explicitly by setting the environment variable ``BTEST_TEST_BASE``.
When setting values for
configuration options, the absolute path to the base directory is
available by using the macro ``%(testbase)s`` (the weird syntax is
due to Python's ``ConfigParser`` class).

Furthermore, all values can use standard "backtick-syntax" to
include the output of external commands (e.g., xyz=`\echo test\`).
Note that the backtick expansion is performed after any ``%(..)``
have already been replaced (including within the backticks).

.. _default: `defaults`_
.. _defaults:

Defaults
~~~~~~~~

There is a special section that can be added to the configuration file that will
set default values to be used during the parsing of other configuration
directives. For example::

    [DEFAULT]
    val=abcd

    [environment]
    ENV_VALUE=%(val)s

The configuration parser reads the keys and values from the DEFAULT section
prior to reading the other sections. It uses those keys to replace the ``%()s``
macros as described earlier. The values stored in these keys can be overridden
at runtime by using the ``-s``/``--set`` command-line argument. For example to
override the ``val`` default above, the ``-s val=other`` argument can be
passed. In that case, ``ENV_VALUE`` would be set to ``other`` instead of
``abcd``.

.. _option: `options`_
.. _options:

Options
~~~~~~~

The following options can be set in the ``btest`` section of the
configuration file:

``BaselineDir``
    One or more directories where to store the baseline files for
    ``btest-diff`` (note that the actual baseline files will be placed
    into test-specific subdirectories of this directory).  By default,
    this is set to ``%(testbase)s/Baseline``.

    If multiple directories are to be used, they must be separated by
    colons. ``btest-diff`` will then search them for baseline files in
    order when looking for a baseline to compare against. When
    updating a baseline, it will always store the new version inside
    the first directory. Using multiple directories is most useful in
    combination with alternatives_ to support alternate executions
    where some tests produce expected differences in their output.

    This option can also be set through an environment variable
    ``BTEST_BASELINE_DIR``.

``CommandPrefix``
    Changes the naming of all ``btest`` commands by replacing the
    ``@TEST-`` prefix with a custom string. For example, with
    ``CommandPrefix=$TEST-``, the ``@TEST-EXEC`` command becomes
    ``$TEST-EXEC``.

``Finalizer``
    A command that will be executed each time any test has
    successfully run. It runs in the same directory as the test itself
    and receives the name of the test as its only argument. The return
    value indicates whether the test should indeed be considered
    successful. By default, there's no finalizer set.

``IgnoreDirs``
    A space-separated list of relative directory names to ignore
    when scanning test directories recursively. Default is empty.

    An alternative way to ignore a directory is placing a file
    ``.btest-ignore`` in it.

``IgnoreFiles``
    A space-separated list of filename globs matching files to
    ignore when scanning given test directories recursively.
    Default is empty.

    An alternative way to ignore a file is by placing ``@TEST-IGNORE``
    in it.

``Initializer``
    A command that will be executed before each test. It runs in
    the same directory as the test itself will and receives the name
    of the test as its only argument. The return value indicates whether
    the test should continue; if false, the test will be considered
    failed. By default, there's no initializer set.

``MinVersion``
    On occasion, you'll want to ensure that the version of ``btest``
    running your testsuite includes a particular feature. By setting
    this value to a given version number (as reported by ``btest
    --version``), ``btest`` installations older than this version will
    fail test execution with exit code 1 and a corresponding error
    message on stderr.

``PartFinalizer``
    A command that will be executed each time a test *part* has
    successfully run. This operates similarly to ``Finalizer`` except
    that it runs after each test part rather than only at completion
    of the full test. See `parts`_ for more about test parts.

``PartInitializer``
    A command that will be executed before each test *part*. This operates
    similarly to ``Initializer`` except that it runs at the beginning of any
    test part that BTest runs. See `parts`_ for more about test parts.

    Since a failing test part aborts execution of the test, part initializers do
    not run for any subsequent skipped parts.

``PartTeardown``
    A command that will run after any test *part* that has run, regardless
    of failure or success of the part. This operates similarly to ``Teardown``
    except it applies to test `parts`_ instead of the full test.

    Since a failing test part aborts execution of the test, part teardowns do
    not run for any subsequent skipped parts.

``PerfPath``
    Specifies a path to the ``perf`` tool, which is used on Linux to
    measure the execution times of tests. By default, BTest searches
    for ``perf`` in ``PATH``.

``PortRange``
    Specifies a port range like "10000-11000" to use in conjunction with
    ``@TEST-PORT`` commands.  Port assignments will be restricted to this
    range.  The default range is "1024-65535".

``StateFile``
    .. _state_file:

    The name of the state file to record the names of failing tests. Default is
    ``.btest.failed.dat``.

``Teardown``
    A command that will be executed each time any test has run, regardless of
    whether that test succeeded. Conceptually, it pairs with an ``Initializer``
    that sets up test infrastructure that requires tear-down at the end of the
    test. It runs in the same directory as the test itself and receives the name
    of the test as its only argument. There's no default teardown command.

    Teardown commands may return a non-zero exit code, which fails the
    corresponding test. Succeeding teardown commands do not override an
    otherwise failing test; such tests will still fail.

    To allow teardown routines to reason about the preceding tests, they
    receive two additional environment variables:

    ``TEST_FAILED``
        This variable is defined (to 1) when the test has failed, and absent
        otherwise.

    ``TEST_LAST_RETCODE``
        This variable contains the numeric exit code of the last command
        run prior to teardown.

``TestDirs``
    A space-separated list of directories to search for tests. If
    defined, one doesn't need to specify any tests on the command
    line.

``TimingBaselineDir``
    A directory where to store the host-specific `timing`_ baseline
    files. By default, this is set to
    ``%(testbase)s/Baseline/_Timing``.

``TimingDeltaPerc``
    A value defining the `timing`_ deviation percentage that's tolerated
    for a test before it's considered failed. Default is 1.0 (which means
    a 1.0% deviation is tolerated by default).

``TmpDir``
    A directory where to create temporary files when running tests.
    By default, this is set to ``%(testbase)s/.tmp``.

.. _environment variables:

Environment Variables
~~~~~~~~~~~~~~~~~~~~~

A special section ``environment`` defines environment variables that
will be propagated to all tests::

     [environment]
     CFLAGS=-O3
     PATH=%(testbase)s/bin:%(default_path)s

Note how ``PATH`` can be adjusted to include local scripts: the
example above prefixes it with a local ``bin/`` directory inside the
base directory, using the predefined ``default_path`` macro to refer
to the ``PATH`` as it is set by default.

Furthermore, by setting ``PATH`` to include the ``btest``
distribution directory, one could skip the installation of the
``btest`` package.

.. _alternative: alternatives_
.. _alternatives:

Alternatives
~~~~~~~~~~~~

BTest can run a set of tests with different settings than it would
normally use by specifying an *alternative* configuration. Currently,
three things can be adjusted:

- Further environment variables can be set that will then be
  available to all the commands that a test executes.

- *Filters* can modify an input file before a test uses it.

- *Substitutions* can modify command lines executed as part of a
  test.

We discuss the three separately in the following. All of them are
defined by adding sections ``[<type>-<name>]`` where ``<type>``
corresponds to the type of adjustment being made and ``<name>`` is the
name of the alternative. Once at least one section is defined for a
name, that alternative can be enabled by BTest's ``--alternative``
flag.

Environment Variables
^^^^^^^^^^^^^^^^^^^^^

An alternative can add further environment variables by defining an
``[environment-<name>]`` section::

    [environment-myalternative]
    CFLAGS=-O3

Running ``btest`` with ``--alternative=myalternative`` will now make
the ``CFLAGS`` environment variable available to all commands
executed.

Prefixing the name of an environment variable with ``-`` in an alternative
section removes the respective variable from the environment::

    [environment-myalternative]
    -CFLAGS=

It is an error to provide a value when prefixing with ``-``.

As a special case, one can override two specific environment
variables---``BTEST_TEST_BASE`` and ``BTEST_BASELINE_DIR``---inside an
alternative's environment section to have them not only be passed on
to child processes, but also apply to the ``btest`` process itself.
That way, one can switch to a different base and baseline directories
for an alternative.

.. _filters:

Filters
^^^^^^^

Filters are a transparent way to adapt the input to a specific test
command before it is executed. A filter is defined by adding a section
``[filter-<name>]`` to the configuration file. This section must have
exactly one entry, and the name of that entry is interpreted as the
name of a command whose input is to be filtered.  The value of that
entry is the name of a filter script that will be run with two
arguments representing input and output files, respectively. Example::

    [filter-myalternative]
    cat=%(testbase)s/bin/filter-cat

Once the filter is activated by running ``btest`` with
``--alternative=myalternative``, every time a ``@TEST-EXEC: cat
%INPUT`` is found, ``btest`` will first execute (something similar to)
``%(testbase)s/bin/filter-cat %INPUT out.tmp``, and then subsequently
``cat out.tmp`` (i.e., the original command but with the filtered
output).  In the simplest case, the filter could be a no-op in the
form ``cp $1 $2``.


    **NOTE:** There are a few limitations to the filter concept currently:

    * Filters are *always* fed with ``%INPUT`` as their first
      argument. We should add a way to filter other files as well.

    * Filtered commands are only recognized if they are directly
      starting the command line. For example, ``@TEST-EXEC: ls | cat
      >output`` would not trigger the example filter above.

    * Filters are only executed for ``@TEST-EXEC``, not for
      ``@TEST-EXEC-FAIL``.

.. _substitution:

Substitutions
^^^^^^^^^^^^^

Substitutions are similar to filters, yet they do not adapt the input
but the command line being executed. A substitution is defined by
adding a section ``[substitution-<name>]`` to the configuration file.
For each entry in this section, the entry's name specifies the
command that is to be replaced with something else given as its value.
Example::

    [substitution-myalternative]
    gcc=gcc -O2

Once the substitution is activated by running ``btest`` with
``--alternative=myalternative``, every time a ``@TEST-EXEC`` executes
``gcc``, that is replaced with ``gcc -O2``. The replacement is simple
string substitution so it works not only with commands but anything
found on the command line; it however only replaces full words, not
subparts of words.

Supported Keywords
------------------

``btest`` scans a test file for lines containing keywords that
trigger certain functionality. It knows the following keywords:

``@TEST-ALTERNATIVE: <alternative>``
    Runs this test only for the given alternative (see alternative_).
    If ``<alternative>`` is ``default``, the test executes when BTest runs
    with no alternative given (which however is the default anyway).

``@TEST-COPY-FILE: <file>``
    Copy the given file into the test's directory before the test is
    run. If ``<file>`` is a relative path, it's interpreted relative
    to the BTest's base directory. Environment variables in ``<file>``
    will be replaced if enclosed in ``${..}``. This command can be
    given multiple times.

``@TEST-DOC: <docstring>``
    Associates a documentation string with the test. These strings
    get included into the output of the ``--documentation`` option.

.. _@TEST-EXEC:

``@TEST-EXEC: <cmdline>``
    Executes the given command line and aborts the test if it
    returns an error code other than zero. The ``<cmdline>`` is
    passed to the shell and thus can be a pipeline, use redirection,
    and any environment variables specified in ``<cmdline>`` will be
    expanded, etc.

    When running a test, the current working directory for all
    command lines will be set to a temporary sandbox (and will be
    deleted later).

    There are two macros that can be used in ``<cmdline>``:
    ``%INPUT`` will be replaced with the full pathname of the file defining
    the test (this file is in a temporary sandbox directory and is a copy
    of the original test file); and ``%DIR`` will be replaced with the full
    pathname of the directory where the test file is located (note that
    this is the directory where the original test file is located, not
    the directory where the ``%INPUT`` file is located). The latter can
    be used to reference further files also located there.

    In addition to environment variables defined in the
    configuration file, there are further ones that are passed into
    the commands:

    ``TEST_BASE``
        The BTest base directory, i.e., the directory where
        ``btest.cfg`` is located.

    ``TEST_BASELINE``
        A list of directories where the command can save permanent
        information across ``btest`` runs. (This is where
        ``btest-diff`` stores its baseline in ``UPDATE`` mode.)

        Multiple entries are separated by colons. If more than one
        entry is given, semantics should be to search them in order.
        (This is where ``btest-diff`` stores its baseline in
        ``UPDATE`` mode.)

    ``TEST_DIAGNOSTICS``
        A file where further diagnostic information can be saved
        in case a command fails (this is also where ``btest-diff``
        stores its diff). If this file exists, then the
        ``--diagnostics-all`` or ``--diagnostics`` options will show
        this file (for the latter option, only if a command fails).

    ``TEST_MODE``
        This is normally set to ``TEST``, but will be ``UPDATE``
        if ``btest`` is run with ``--update-baseline``, or
        ``UPDATE_INTERACTIVE`` if run with ``--update-interactive``.

    ``TEST_NAME``
        The name of the currently executing test.

    ``TEST_PART``
        The test part number (see `parts`_ for more about test parts).

          **NOTE:**

          If a command returns the special exit code 100, the test is
          considered failed, however subsequent test commands within the
          current test are still run. ``btest-diff`` uses this special
          exit code to indicate that no baseline has yet been established.

          If a command returns the special exit code 200, the test is
          considered failed and all further tests are aborted.
          ``btest-diff`` uses this special exit code when ``btest`` is run
          with the ``--update-interactive`` option and the user chooses to
          abort the tests when prompted to record a new baseline.

    ``TEST_VERBOSE``
        The path of a file where the test can record further
        information about its execution that will be included with
        BTest's ``--verbose`` output. This is for further tracking
        the execution of commands and should generally generate
        output that follows a line-based structure.


``@TEST-EXEC-FAIL: <cmdline>``
    Like ``@TEST-EXEC``, except that this expects the command to
    *fail*, i.e., the test is aborted when the return code is zero.

.. _@TEST-GROUP:

``@TEST-GROUP: <group>``
    Assigns the test to a group of name ``<group>``. By using option
    ``-g`` one can limit execution to all tests that belong to a given
    group (or a set of groups).

``@TEST-IGNORE``
    This is used to indicate that this file should be skipped (i.e., no
    test commands in this file will be executed).  An alternative way to
    ignore files is by using the ``IgnoreFiles`` option in the btest
    configuration file.

``@TEST-KNOWN-FAILURE``
   Marks a test as known to currently fail. This only changes BTest's
   output, which upon failure will indicate that that is expected; it
   won't change the test's processing otherwise. The keyword doesn't
   take any arguments but one could add a descriptive text, as in ::

    .. @TEST-KNOWN-FAILURE: We know this fails because ....

.. _@TEST-MEASURE-TIME:

``@TEST-MEASURE-TIME``
   Measures execution time for this test and compares it to a
   previously established `timing`_ baseline. If it deviates significantly,
   the test will be considered failed.

``@TEST-NOT-ALTERNATIVE: <alternative>``
    Ignores this test for the given alternative (see alternative_).
    If ``<alternative>`` is ``default``, the test is ignored if BTest runs
    with no alternative given.

.. _@TEST-PORT:

``@TEST-PORT: <env>``
   Assign an available TCP port number to an environment variable
   that is accessible from the running test process.  ``<env>`` is an
   arbitrary user-chosen string that will be set to the next available
   TCP port number.  Availability is based on checking successful
   binding of the port on IPv4 INADDR_ANY and also restricted to the
   range specified by the ``PortRange`` option.  IPv6 is not supported.
   Note that using the ``-j`` option to parallelize execution will
   work such that unique/available port numbers are assigned between
   concurrent tests, however there is still a potential race condition
   for external processes to claim a port before the test actually
   runs and claims it for itself.

``@TEST-REQUIRES: <cmdline>``
    Defines a condition that must be met for the test to be executed.
    The given command line will be run before any of the actual test
    commands, and it must return success for the test to continue. If
    it does not return success, the rest of the test will be skipped
    but doing so will not be considered a failure of the test. This allows to
    write conditional tests that may not always make sense to run, depending
    on whether external constraints are satisfied or not (say, whether
    a particular library is available). Multiple requirements may be
    specified and then all must be met for the test to continue.

.. _@TEST-SERIALIZE:

``@TEST-SERIALIZE: <set>``
   When using option ``-j`` to parallelize execution, all tests that
   specify the same serialization set are guaranteed to run
   sequentially. ``<set>`` is an arbitrary user-chosen string.

``@TEST-START-FILE <file>``
    This is used to include an additional input file for a test
    right inside the test file. All lines following the keyword line
    will be written into the given file until a line containing
    ``@TEST-END-FILE`` is found.  The lines containing ``@TEST-START-FILE``
    and ``@TEST-END-FILE``, and all lines in between, will be removed from
    the test's %INPUT.  Example::

        > cat examples/t6.sh
        # @TEST-EXEC: awk -f %INPUT <foo.dat >output
        # @TEST-EXEC: btest-diff output

            { lines += 1; }
        END { print lines; }

        @TEST-START-FILE foo.dat
        1
        2
        3
        @TEST-END-FILE

        > btest -D examples/t6.sh
        examples.t6 ... ok
          % cat .diag
          == File ===============================
          3

    Multiple such files can be defined within a single test.

    Note that this is only one way to use further input files.
    Another is to store a file in the same directory as the test
    itself, making sure it's ignored via ``IgnoreFiles``, and then
    refer to it via ``%DIR/<name>``.

``@TEST-START-NEXT``
    This keyword lets you define multiple test inputs in the
    same file, all executing with the same command lines. See
    `defining multiple tests in one file`_ for details.

.. _test selection: `selecting tests`_
.. _selecting tests:

Selecting Tests
===============

Internally, ``btest`` uses logical names for tests, abstracting input
files. Those names result from substituting path separators with dots,
ignoring btest file suffixes, and potentially adding additional
labeling. ``btest`` does this only for tests within the ``TestDirs``
directories given in the `configuration file`.

In addition to the invocations covered in `Running BTest`_, you can
use logical names when telling ``btest`` which tests to run. For
example, instead of saying ::

    > btest testsuite/foo.sh

you can use::

    > btest testsuite.foo

This distinction rarely matters, but it's something to be aware of
when `defining multiple tests in one file`_, which we cover next.

.. _more than one test: `defining multiple tests in one file`_
.. _defining multiple tests in one file:

Defining Multiple Tests in one File
===================================

On occasion you want to use the same constellation of keywords on a
set of input files. BTest supports this via the ``@TEST-START-NEXT``
keyword. When ``btest`` encounters this keyword, it initially
considers the input file to end at that point, and runs all
``@TEST-EXEC-*`` with an ``%INPUT`` truncated accordingly.
Afterwards, it creates a *new* ``%INPUT`` with everything *following*
the ``@TEST-START-NEXT`` marker, running the *same* commands
again. (It ignores any ``@TEST-EXEC-*`` lines later in the file.)

The effect is that a single file can define multiple tests that the
``btest`` output will enumerate::

        > cat examples/t5.sh
        # @TEST-EXEC: cat %INPUT | wc -c >output
        # @TEST-EXEC: btest-diff output

        This is the first test input in this file.

        # @TEST-START-NEXT

        ... and the second.

        > ./btest -D examples/t5.sh
        examples.t5 ... ok
          % cat .diag
          == File ===============================
          119
          [...]

        examples.t5-2 ... ok
          % cat .diag
          == File ===============================
          22
          [...]

``btest`` automatically generates the ``-<n>`` suffix for each of the tests.

    **NOTE:** It matters how you name tests when running them
    individually. When you specify the btest file ("``examples/t5.sh``"),
    ``btest`` will run all of the contained tests. When you use the
    logical name, ``btest`` will run only that specific test: in the
    above scenario, ``examples.t5`` runs only the first test defined
    in the file, while ``examples.t5-2`` only runs the second. This
    also applies to baseline updates.

.. _parts: `splitting tests into parts`_
.. _splitting tests into parts:

Splitting Tests into Parts
==========================

One can also split a single test across multiple files by adding a
numerical ``#<n>`` postfix to their names, where each ``<n>``
represents a separate part of the test. ``btest`` will combine all of
a test's parts in numerical order and execute them subsequently within
the same sandbox. Example::

        > cat examples/t7.sh#1
        # @TEST-EXEC: echo Part 1 - %INPUT >>output

        > cat examples/t7.sh#2
        # @TEST-EXEC: echo Part 2 - %INPUT >>output

        > cat examples/t7.sh#3
        # @TEST-EXEC: btest-diff output

        > btest -D examples/t7.sh
        examples.t7 ... ok
        % cat .diag
        == File ===============================
        Part 1 - /Users/robin/bro/docs/aux/btest/.tmp/examples.t7/t7.sh#1
        Part 2 - /Users/robin/bro/docs/aux/btest/.tmp/examples.t7/t7.sh#2

Note how ``output`` contains the output of both ``t7.sh#1`` and ``t7.sh#2``,
however in each case ``%INPUT`` refers to the corresponding part. For
the first part of a test, one can also omit the ``#1`` postfix in the filename.

.. _canonifiers: `canonifying diffs`_
.. _canonifying diffs:

Canonifying Diffs
=================

``btest-diff`` has the capability to filter its input through an
additional script before it compares the current version with the
baseline. This can be useful if certain elements in an output are
*expected* to change (e.g., timestamps). The filter can then
remove/replace these with something consistent. To enable such
canonification, set the environment variable
``TEST_DIFF_CANONIFIER`` to a script reading the original version
from stdin and writing the canonified version to stdout.
For examples of canonifier scripts, take a look at those `used in the
Zeek distribution <https://github.com/zeek/zeek/tree/master/testing/scripts/>`_.

    **NOTE:** ``btest-diff`` passes both the pre-recorded baseline and
    the fresh test output through any canonifiers before comparing
    their contents. BTest version 0.63 introduced two changes in
    ``btest-diff``'s baseline handling:

    * ``btest-diff`` now records baselines in canonicalized form. The
      benefit here is that by canonicalizing upon recording, you can
      use ``btest -U`` more freely, keeping expected noise out of
      revision control. The downside is that updates to canonifiers
      require a refresh of the baselines.

    * ``btest-diff`` now prefixes the baselines with a header that
      warns against manual modification, and knows to exclude that
      header from comparison. We recommend only ever updating
      baselines via ``btest -U`` (or its interactive sibling, ``-u``).

    Once you use canonicalized baselines in your project, it's a good
    idea to use ``MinVersion = 0.63`` in your btest.cfg to avoid the
    use of older ``btest`` installations. Since these are unaware of
    the new baseline header and repeated application of canonifiers
    may cause unexpected alterations to already-canonified baselines,
    using such versions will likely cause test failures.

Binary Data in Baselines
========================

``btest`` baselines usually consist of text files, i.e. content that
mostly makes sense to process line by line. It's possible to use
binary data as well, though. For such data, ``btest-diff`` supports a
binary mode in which it will treat the baselines as binary "blobs". In
this mode, it will compare test output to baselines for byte-by-byte
equality only, it will never apply any canonifiers, and it will leave
the test output untouched during baseline updates.

To use binary mode, invoke ``btest-diff`` with the ``--binary`` flag.

Running Processes in the Background
===================================

Sometimes processes need to be spawned in the background for a test,
in particular if multiple processes need to cooperate in some fashion.
``btest`` comes with two helper scripts to make life easier in such a
situation:

``btest-bg-run <tag> <cmdline>``
    This is a script that runs ``<cmdline>`` in the background, i.e.,
    it's like using ``cmdline &`` in a shell script. Test execution
    continues immediately with the next command. Note that the spawned
    command is *not* run in the current directory, but instead in a
    newly created sub-directory called ``<tag>``. This allows
    spawning multiple instances of the same process without needing to
    worry about conflicting outputs. If you want to access a command's
    output later, like with ``btest-diff``, use ``<tag>/foo.log`` to
    access it.

``btest-bg-wait [-k] <timeout>``
    This script waits for all processes previously spawned via
    ``btest-bg-run`` to finish. If any of them exits with a non-zero
    return code, ``btest-bg-wait`` does so as well, indicating a
    failed test. ``<timeout>`` is mandatory and gives the maximum
    number of seconds to wait for any of the processes to terminate.
    If any process hasn't done so when the timeout expires, it will be
    killed and the test is considered to be failed as long as ``-k``
    is not given. If ``-k`` is given, pending processes are still
    killed but the test continues normally, i.e., non-termination is
    not considered a failure in this case. This script also collects
    the processes' stdout and stderr outputs for diagnostics output.


.. _progress:

Displaying Progress
===================

For long-running tests it can be helpful to display progress messages
during their execution so that one sees where the test is currently
at. There's a helper script, `btest-progress`, to facilitate that. The
script receives a custom message as its sole argument. When executed
while a test is running, ``btest`` will display that message in real-time
in its standard and verbose outputs.

Example usage::

        # @TEST-EXEC: bash %INPUT

        btest-progress Stage 1
        sleep 1
        btest-progress Stage 2
        sleep 1
        btest-progress Stage 3
        sleep 1

When the tests execute, ``btest`` will then show these three messages
successively. By default, ``btest-progress`` also prints the messages
to the test's standard output and standard error. That can be suppressed by
adding an option ``-q`` to the invocation.

.. _timing: `timing execution`_
.. _timing execution:

Timing Execution
================

``btest`` can time execution of tests and report significant
deviations from past runs. As execution time is inherently
system-specific it keeps separate per-host timing baselines for that.
Furthermore, as time measurements tend to make sense only for
individual, usually longer running tests, they are activated on per
test basis by adding a `@TEST-MEASURE-TIME`_ directive. The test
will then execute as usual yet also record the duration for which it
executes. After the timing baselines are created (with the ``--update-times``
option), further runs on the same host will compare their times against that
baseline and declare a test failed if it deviates by more than, by
default, 1%. (To tune the behaviour, look at the ``Timing*`` `options`_.)
If a test requests measurement but BTest can't find a timing baseline
or the necessary tools to perform timing measurements, then it will
ignore the request.

As timing for a test can deviate quite a bit even on the same host,
BTest does not actually measure *time* but the number of CPU
instructions that a test executes, which tends to be more stable.
That however requires the right tools to be in place. On Linux, BTest
leverages `perf <https://perf.wiki.kernel.org>`_.  By default, BTest
will search for ``perf`` in the ``PATH``; you can specify a different
path to the binary by setting ``PerfPath`` in ``btest.cfg``.


Integration with Sphinx
=======================

``btest`` comes with an extension module for the documentation framework
`Sphinx <http://sphinx.pocoo.org>`_. The extension module provides two
new directives called ``btest`` and ``btest-include``.  The ``btest``
directive allows writing a test directly inside a Sphinx document, and
then the output from the test's command is included in the generated
documentation. The ``btest-include`` directive allows for literal text
from another file to be included in the generated documentation.
The tests from both directives can also be run externally and will catch
if any changes to the included content occur. The following walks
through setting this up.

Configuration
-------------

First, you need to tell Sphinx a base directory for the ``btest``
configuration as well as a directory in there where to store tests
it extracts from the Sphinx documentation. Typically, you'd just
create a new subdirectory ``tests`` in the Sphinx project for the
``btest`` setup and then store the tests in there in, e.g.,
``doc/``::

    > cd <sphinx-root>
    > mkdir tests
    > mkdir tests/doc

Then add the following to your Sphinx ``conf.py``::

    extensions += ["btest-sphinx"]
    btest_base="tests"         # Relative to Sphinx-root.
    btest_tests="doc"          # Relative to btest_base.

Next, create a ``btest.cfg`` in ``tests/`` as usual and add
``doc/`` to the ``TestDirs`` option.  Also, add a finalizer to ``btest.cfg``::

    [btest]
    ...
    PartFinalizer=btest-diff-rst


Including a Test into a Sphinx Document
---------------------------------------

The ``btest`` extension provides a new directive to include a test
inside a Sphinx document::


    .. btest:: <test-name>

        <test content>

Here, ``<test-name>`` is a custom name for the test; it will be
stored in ``btest_tests`` under that name (with a file extension of
``.btest``). ``<test content>`` is just a standard test as you would
normally put into one of the ``TestDirs``. Example::


    .. btest:: just-a-test

        @TEST-EXEC: expr 2 + 2

When you now run Sphinx, it will (1) store the test content into
``tests/doc/just-a-test.btest`` (assuming the above path layout), and (2)
execute the test by running ``btest`` on it. You can then run
``btest`` manually in ``tests/`` as well and it will execute the test
just as it would in a standard setup. If a test fails when Sphinx runs
it, there will be a corresponding error and include the diagnostic output
into the document.

By default, nothing else will be included into the generated
documentation, i.e., the above test will just turn into an empty text
block. However, ``btest`` comes with a set of scripts that you can use
to specify content to be included. As a simple example,
``btest-rst-cmd <cmdline>`` will execute a command and (if it
succeeds) include both the command line and the standard output into
the documentation. Example::

    .. btest:: another-test

        @TEST-EXEC: btest-rst-cmd echo Hello, world!

When running Sphinx, this will render as::

    # echo Hello, world!
    Hello, world!


The same ``<test-name>`` can be used multiple times, in which case
each entry will become one part of a joint test. ``btest`` will
execute all parts subsequently within a single sandbox, and earlier
results will thus be available to later parts.

When running ``btest`` manually in ``tests/``, the ``PartFinalizer`` we
added to ``btest.cfg`` (see above) compares the generated reST code
with a previously established baseline, just like ``btest-diff`` does
with files. To establish the initial baseline, run ``btest -u``, like
you would with ``btest-diff``.

Scripts
-------

The following Sphinx support scripts come with ``btest``:

``btest-rst-cmd [options] <cmdline>``

By default, this executes ``<cmdline>`` and includes both the
command line itself and its standard output into the generated
documentation (but only if the command line succeeds).
See above for an example.

This script provides the following options:

-c ALTERNATIVE_CMDLINE
    Show ``ALTERNATIVE_CMDLINE`` in the generated
    documentation instead of the one actually executed. (It
    still runs the ``<cmdline>`` given outside the option.)

-d
    Do not actually execute ``<cmdline>``; just format it for
    the generated documentation and include no further output.

-f FILTER_CMD
    Pipe the command line's output through ``FILTER_CMD``
    before including. If ``-r`` is given, it filters the
    file's content instead of stdout.

-n N
    Include only ``N`` lines of output, adding a ``[...]`` marker if
    there's more.

-o
    Do not include the executed command into the generated
    documentation, just its output.

-r FILE
    Insert ``FILE`` into output instead of stdout. The ``FILE`` must
    be created by a previous ``@TEST-EXEC`` or ``@TEST-COPY-FILE``.


``btest-rst-include [options] <file>``

Includes ``<file>`` inside a code block.  The ``<file>`` must be created
by a previous ``@TEST-EXEC`` or ``@TEST-COPY-FILE``.

This script provides the following options:

-n N
    Include only ``N`` lines of output, adding a ``[...]`` marker if
    there's more.


``btest-rst-pipe <cmdline>``

Executes ``<cmdline>``, includes its standard output inside a code
block (but only if the command line succeeds). Note that
this script does not include the command line itself into the code
block, just the output.

    **NOTE:** All these scripts can be run directly from the command
    line to show the reST code they generate.

    **NOTE:** ``btest-rst-cmd`` can do everything the other scripts
    provide if you give it the right options. In fact, the other
    scripts are provided just for convenience and leverage
    ``btest-rst-cmd`` internally.

Including Literal Text
----------------------

The ``btest`` Sphinx extension module also provides a directive
``btest-include`` that functions like ``literalinclude`` (including all
its options) but also creates a test checking the included content for
changes. As one further extension, the directive expands environment
variables of the form ``${var}`` in its argument.  Example::

    .. btest-include:: ${var}/path/to/file

When you now run Sphinx, it will automatically generate a test
file in the directory specified by the ``btest_tests`` variable in
the Sphinx ``conf.py`` configuration file.  In this example, the filename
would be ``include-path_to_file.btest`` (it automatically adds a prefix of
"include-" and a file extension of ".btest").  When you run
the tests externally, the tests generated by the ``btest-include``
directive will check if any of the included content has changed (you'll
first need to run ``btest -u`` to establish the initial baseline).


License
=======

BTest is open-source under a BSD license.
