Environment and CLI
===================

Tests built with Criterion expose by default various command line switchs
and environment variables to alter their runtime behaviour.

Command line arguments
----------------------

* ``-h or --help``: Show a help message with the available switches.
* ``-q or --quiet``: Disables all logging.
* ``-v or --version``: Prints the version of criterion that has been
  linked against.
* ``-l or --list``: Print all the tests in a list.
* ``-f or --fail-fast``: Exit after the first test failure.
* ``--ascii``: Don't use fancy unicode symbols or colors in the output.
* ``-jN or --jobs N``: Use ``N`` parallel jobs to run the tests. ``0`` picks
  a number of jobs ideal for your hardware configuration.
* ``--filter [PATTERN]``: Run tests whose string identifier matches
  the given shell wildcard pattern (see dedicated section below). (\*nix only)
* ``--debug[=debugger]``: Run tests with a debugging server attached.
  ``debugger`` can be 'gdb', 'lldb', or 'windbg' (windows only).
* ``--debug-transport [TRANSPORT]``: Make the debugging server use the
  specified remote transport. Only transports of the form ``tcp:port`` are
  currently supported. ``tcp:1234`` is the default.
* ``--no-early-exit``: This flag is deprecated and no longer does anything.
* ``-S or --short-filename``: The filenames are displayed in their short form.
* ``--always-succeed``: The process shall exit with a status of ``0``.
* ``--tap[=FILE]``: Writes a TAP (Test Anything Protocol) report to FILE.
  No file or ``"-"`` means ``stderr`` and implies ``--quiet``. This option is
  equivalent to ``--output=tap:FILE``.
* ``--xml[=FILE]``: Writes JUnit4 XML report to FILE.
  No file or ``"-"`` means ``stderr`` and implies ``--quiet``. This option is
  equivalent to ``--output=tap:FILE``.
* ``--json[=FILE]``: Writes a JSON report to FILE.
  No file or ``"-"`` means ``stderr`` and implies ``--quiet``. This option is
  equivalent to ``--output=tap:FILE``.
* ``--verbose[=level]``: Makes the output verbose. When provided with an integer,
  sets the verbosity level to that integer.
* ``-OPROVIDER:FILE or --output=PROVIDER:FILE``: Write a test report to FILE
  using the output provider named by PROVIDER.
  If FILE is ``"-"``, it implies ``--quiet``, and the report shall be written
  to ``stderr``.

Shell Wildcard Pattern
----------------------

Extglob patterns in criterion are matched against a test's string identifier.

In the table below, a ``pattern-list`` is a list of patterns separated by ``|``.
Any extglob pattern can be constructed by combining any of the following
sub-patterns:

==================== ======================================================
Pattern              Meaning
==================== ======================================================
``*``                matches everything
-------------------- ------------------------------------------------------
``?``                matches any character
-------------------- ------------------------------------------------------
``[seq]``            matches any character in *seq*
-------------------- ------------------------------------------------------
``[!seq]``           matches any character not in *seq*
-------------------- ------------------------------------------------------
``?(pattern-list)``  Matches zero or one occurrence of the given patterns
-------------------- ------------------------------------------------------
``*(pattern-list)``  Matches zero or more occurrences of the given patterns
-------------------- ------------------------------------------------------
``+(pattern-list)``  Matches one or more occurrences of the given patterns
-------------------- ------------------------------------------------------
``@(pattern-list)``  Matches one of the given patterns
-------------------- ------------------------------------------------------
``!(pattern-list)``  Matches anything except one of the given patterns
==================== ======================================================

A test string identifier is of the form ``suite-name/test-name``, so a pattern
of ``simple/*`` matches every tests in the ``simple`` suite, ``*/passing``
matches all tests named ``passing`` regardless of the suite, and ``*`` matches
every possible test.

Environment Variables
---------------------

Environment variables are alternatives to command line switches when set to 1.

* ``CRITERION_ALWAYS_SUCCEED``:  Same as ``--always-succeed``.
* ``CRITERION_FAIL_FAST``:       Same as ``--fail-fast``.
* ``CRITERION_USE_ASCII``:       Same as ``--ascii``.
* ``CRITERION_JOBS``:            Same as ``--jobs``. Sets the number of jobs to
  its value.
* ``CRITERION_SHORT_FILENAME``:  Same as ``--short-filename``.
* ``CRITERION_VERBOSITY_LEVEL``: Same as ``--verbose``. Sets the verbosity level
  to its value.
* ``CRITERION_TEST_PATTERN``:    Same as ``--pattern``. Sets the test pattern
  to its value. (\*nix only)
* ``CRITERION_DISABLE_TIME_MEASUREMENTS``: Disables any time measurements on
  the tests.
* ``CRITERION_OUTPUTS``:         Can be set to a comma-separated list of
  ``PROVIDER:FILE`` entries. For instance, setting the variable to
  ``tap:foo.tap,xml:bar.xml`` has the same effect as specifying ``--tap=foo.tap``
  and ``--xml=bar.xml`` at once.
* ``CRITERION_ENABLE_TAP``:      (Deprecated, use CRITERION_OUTPUTS) Same as ``--tap``.