pbbt 0.2.0
Pluggable Black-Box Testing toolkit
License: MIT

***********************************************
  PBBT -- Pluggable Black-Box Testing toolkit
***********************************************

.. contents:: Table of Contents


Overview
========

PBBT is a regression test harness for *black-box testing*.  It is
suitable for testing complex software components with well-defined input
and output interfaces.

::

      input    +----------+   output
    o--------> | Software | --------->o
               +----------+

In black-box testing, a *test case* is a combination of *input* and
expected *output* data.  The test harness executes the software with the
given input and verifies that the produced output coincides with the
expected output.

Black-box testing could be implemented for many different types of
software.  For example,

* *a database system:* the input is a SQL statement, the output is a set
  of records;
* *a web service:* the input is an HTTP request, the output is an HTTP
  response;
* *a command-line utility:* the input is a sequence of command-line
  parameters and ``stdin``, the output is ``stdout``;
* *a GUI application:* different approaches are possible; for instance,
  the input could be a sequence of user actions, and the output could be
  the state of a particular widget.

PBBT is a Python library and an application which allows you to:

* use built-in test types for testing command-line scripts and Python
  code;
* register custom test types;
* prepare test input in a succinct YAML_ format;
* in the *train* mode, run the test cases and record expected output;
* in the *check* mode, run the test cases and verify that the produced
  output coincides with the pre-recorded expected output.

PBBT is a free software released under MIT license.  PBBT is created by
Clark C. Evans and Kirill Simonov from `Prometheus Research, LLC`_.


Using PBBT
==========

To install PBBT, you can use pip_ package manager::

    # pip install pbbt

This command downloads and installs the latest version of PBBT from
`Python Package Index`_.  After successful installation, you should be
able to import ``pbbt`` Python module and run ``pbbt`` command-line
utility.

To start using PBBT, you need to create a file with input data.  For
example, create ``input.yaml`` with the following content::

    py: |
      print "Hello, World!"

This file is in YAML_ format, which is a data serialization language
similar to JSON_, and, in fact, a superset of JSON.  The file above
could be represented in JSON as::

    { "py": "print \"Hello, World!\"\n" }

For description of YAML syntax and semantics, see http://yaml.org/.

Next, execute PBBT in *training* mode to generate expected output data.
Run::

    $ pbbt input.yaml output.yaml --train

and accept new output when asked.  PBBT will write output data to
``output.yaml``::

    py: print-hello-world
    stdout: |
      Hello, World!

Now you can start PBBT in *checking* mode, in which it executes test
cases and verifies that expected and actual output data coincide::

    $ pbbt input.yaml output.yaml

To add more test cases to ``input.yaml``, you need to convert it to a
*test suite*::

    title: My Tests
    tests:
    - py: |
        print "Hello, World!"
    - sh: echo Hello, World!

The file now contains a test suite *My Tests* with two test cases: one
as in the previous example, and another that executes a shell command
``echo Hello, World!``::

    sh: echo Hello, World!

The output of this test case is ``stdout`` produced by the shell
command.  To record expected output, run ``pbbt`` in training mode
again.


Built-in Test Types
===================

Out of the box, PBBT supports a small set of predefined test types:

* test Python code;
* test a shell command;
* file manipulation tests.

Also available are special test types:

* test suite;
* include;
* conditional variables.
* gateway to other test systems.

Each test type defines the structure of input and output records, that
is, the set of mandatory and optional fields and the type of field
values.  In this section, we list all available test types and describe
their input fields.

Common Fields
-------------

The following optional fields are available for all test types where
they make sense:

``skip``: ``true`` or ``false``
    On ``true``, skip this test case.

``if``: variable, list of variables or Python expression
    On a *variable name*, run this test case only if the variable is
    defined and not false.

    On a *list of variables*, run this test case only if at least one
    variable is defined and not false.

    On a *Python expression*, run this test case if the expression
    evaluates to true.  You can use any conditional variables in the
    expression.

``unless``: variable, list of variables or Python expression
    On a *variable name*, skip this test case if the variable is defined
    and not false.

    On a *list of variables*, skip this test case if at least one
    variable is defined and not false.

    On a *Python expression*, skip this test case if the expression
    evaluates to true.  You can use any conditional variables in the
    expression.

``ignore``: ``true``, ``false`` or regular expression
    On ``true``, permit the actual and expected output to be unequal.
    The test case must still execute without any errors.

    On a *regular expression*, pre-process the actual and expected
    output before comparing them:

    1. Run the regular expression against the output data and find
       all matches.
    2. If the regular expression does not contain ``()`` subgroups,
       erase all the matches from the output.
    3. If the regular expression contains one or more ``()`` subgroups,
       erase the content of the subgroups from the output.

    The regular expression is compiled with ``MULTILINE`` and
    ``VERBOSE`` flags.

Example::

    title: Integration with MySQL
    if: has_mysql
    tests:
    - set:
        MYSQL_HOST: localhost
        MYSQL_PORT: 3306
      unless: [MYSQL_HOST, MYSQL_PORT]
    - read: /etc/mysql/my.cnf
      if: MYSQL_HOST == 'localhost'
    - py: test-scalar-types.py
      ignore: |
        ^Today:.(\d\d\d\d)-(\d\d)-(\d\d)$
    - py: test-array-types.py
      skip: true    # No array type in MySQL

Test Suite
----------

A test suite is a collection of test cases.

A suite may contain other suites and thus all test suites form a tree
structure.  A *path* formed from suite identifiers can uniquely locate
any suite.  We use file-system notation for suite paths (e.g.
``/path/to/suite``).

Fields:

``title``: text
    The title of the suite.

``suite``: identifier (optional)
    The identifier of the suite.  If not set, generated from the title.

``tests``: list of input records
    The content of the suite.

``output``: path (optional)
    If set, the expected output of the suite is loaded from the given
    file.

Example::

    title: All Tests
    suite: all
    output: output.yaml
    tests:
    - py: ./test/core.py
    - py: ./test/ext.py
    - title: Database Tests
      tests:
      - py: ./test/sqlite.py
      - py: ./test/pgsql.py
      - py: ./test/mysql.py

In this example, the path to the *Database Tests* suite is
``/all/database-tests``.

Conditional Variables
---------------------

This test case defines a conditional variable.

Variables could be used in ``if`` and ``unless`` clauses to
conditionally enable or disable a test case.  Variables could also be
set or read in Python tests via a global dictionary ``__pbbt__``.

Conditional variables could also be set from command line using ``-D``
option.

Setting a conditional variable affects all subsequent test cases within
the same test suite.  Variable values are reset on exit from the suite.

Fields:

``set``: variable or dictionary of variables
    On a *variable name*, set the value of the given variable to
    ``True``.

    On a *dictionary*, set the values of the given variables.

Example::

    title: MySQL Tests
    tests:
    - set: MYSQL
    - set:
        MYSQL_HOST: localhost
        MYSQL_PORT: 3306
      unless: [MYSQL_HOST, MYSQL_PORT]
    - py: |
        # Determine the version of the MySQL server
        import MySQLdb
        connection = MySQLdb.connect(host=__pbbt__['MYSQL_HOST'],
                                     port=int(__pbbt__['MYSQL_PORT']),
                                     db='mysql')
        cursor = connection.cursor()
        cursor.execute("""SELECT VERSION()""")
        version_string = cursor.fetchone()[0]
        version = tuple(map(int, version_string.split('-')[0].split('.')))
        __pbbt__['MYSQL_VERSION'] = version
    - py: test-ddl.py
    - py: test-dml.py
    - py: test-select.py
    - py: test-new-features.py
      if: MYSQL_VERSION >= (5, 5)

Include Test
------------

This test case loads and executes a test case from a file.

Fields:

``include``: path
    The file to load.  The file should contain an input test record in
    YAML format.

Example::

    title: All Tests
    tests:
    - include: test/core.yaml
    - include: test/ext.yaml
    - include: test/sqlite.yaml
    - include: test/pgsql.yaml
    - include: test/mysql.yaml

Python Code
-----------

This test case executes Python code and produces ``stdout``.

Fields:

``py``: path or Python code
    On *Python code*, the source code to execute.

    On a *file name*, the file which contains source code to execute.

``stdin``: text (optional)
    Content of the standard input.

``except``: exception type (optional)
    If set, indicates that the code is expected to raise an exception of
    the given type.

Example::

    title: Python tests
    tests:
    - py: hello.py
    - py: &sum |
        # Sum of two numbers
        import sys
        a = int(sys.stdin.readline())
        b = int(sys.stdin.readline())
        c = a+b
        sys.stdout.write("%s\n" % c)
      stdin: |
        2
        2
    - py: *sum
      stdin: |
        1
        -5
    - py: *sum
      stdin: |
        one
        three
      except: ValueError

Note that we use a YAML anchor (denoted by ``&sum``) and aliases
(denoted by ``*sum``) to use the same piece of code in several tests.

Shell Command
-------------

This test case executes a shell command and produces ``stdout``.

Fields:

``sh``: command or executable with a list of parameters
    The shell command to execute.

``stdin``: text (optional)
    Content of the standard input.

``cd``: path (optional)
    Change the current working directory to the given path before
    executing the command.

``environ``: dictionary of variables (optional)
    Add the given variables to the command environment.

``exit``: integer (optional)
    The expected exit code; ``0`` by default.

Example::

    title: Shell tests
    tests:
    - sh: echo Hello, World!
    - sh: cat
      stdin: |
        Hello, World!
    - sh: [cat, /etc/shadow]
      exit: 1   # Permission denied

Write to File
-------------

This test case creates a file with the given content.

Fields:

``write``: path
    The file to create.

``data``: text
    The file content.

Example::

    write: test/tmp/data.txt
    data: |
        Hello, World!

Read from File
--------------

The output of this test is the content of a file.

Fields:

``read``: path
    The file to read.

Example::

    read: test/tmp/data.txt

Remove File
-----------

This test case removes a file.  It is not an error if the file does not
exist.

Fields:

``rm``: path or list of paths
    File(s) to remove.

Example::

    rm: test/tmp/data.txt

Make Directory
--------------

This test case creates a directory.

Parent directories are also created if necessary.  It is not an error if
the directory already exists.

Fields:

``mkdir``: path
    The directory to create.

Example::

    mkdir: test/tmp

Remove Directory
----------------

This test case removes a directory with all its content.

It is not an error if the directory does not exist.

Fields:

``rmdir``: path
    The directory to delete.

Example::

    rmdir: test/tmp

Doctest
-------

This test case executes ``doctest`` on a set of files.

Fields:

``doctest``: path pattern
    Files with doctest sessions.

Example::

    doctest: test/test_*.rst

Unittest
--------

This test case executes ``unittest`` test suite.

Fields:

``unittest``: path pattern
    Files with unittest tests.

Example::

    unittest: test/test_*.py


Pytest
------

This test case executes ``py.test`` test suite.

Package ``pytest`` from http://pytest.org/ must be installed.

Fields:

``pytest``: path pattern
    Files with py.test tests.

Example::

    pytest: test/test_*.py

Coverage
--------

This test case starts coverage of Python code.

Package ``coverage`` from http://nedbatchelder.com/code/coverage/ must
be installed.

Fields:

``coverage``: file name or ``None``
    Path to the configuration file.

``data_file``: file name
    Where to save coverage data.

``timid``: ``false`` or ``true`` (optional)
    Use a simpler trace function.

``branch``: ``false`` or ``true`` (optional)
    Enable branch coverage.

``source``: file paths of package names (optional)
    Source files or packages to measure.

``include``: file patterns
    Files to measure.

``omit``: file patterns
    Files to omit.

Example::

    coverage:
    source: pbbt
    branch: true

Coverage check
--------------

This test case stops coverage and reports measurement summary.

Fields:

``coverage-check``: float
    Expected coverage percentage.

Example::

    coverage-check: 99.0

Coverage report
---------------

This test case stops coverage and saves coverage report to a file.

Fields:

``coverage-report``: directory
    Where to save the report.

Example::

    coverage-report: coverage


Custom Test Types
=================

In this section, we discuss how to add custom test types to PBBT.

Suppose we want to test a SQL database by running a series of SQL
queries and validating that we get expected output.  To implement this
testing scheme, we need a way to:

* open a connection to the database;
* execute a SQL statement and produce a sequence of records.

The input file may look like this::

    title: Database tests
    tests:
    # Remove the database file left after the last testing session.
    - rm: test.sqlite
    # Create a new SQLite database.
    - connect: test.sqlite
    # Run a series of SQL commands.
    - sql: |
        SELECT 'Hello, World!';
    - sql: |
        CREATE TABLE student (
            id      INTEGER PRIMARY KEY,
            name    TEXT NOT NULL,
            gender  CHAR(1) NOT NULL
                    CHECK (gender in ('f', 'i', 'm')),
            dob     DATE NOT NULL
        );
    - sql: |
        INSERT INTO student (id, name, gender, dob)
        VALUES (1001, 'Linda Wright', 'f', '1988-10-03'),
               (1002, 'Beth Thompson', 'f', '1988-01-24'),
               (1003, 'Mark Melton', 'm', '1984-06-05'),
               (1004, 'Judy Flynn', 'f', '1986-09-02'),
               (1005, 'Jonathan Bouchard', 'm', '1982-02-12');
    - sql: |
        SELECT *
        FROM student
        ORDER BY dob;
    - sql: |
        SELECT name
        FROM student
        WHERE id = 1003;

In this input file, we use two new types of test cases:

``connect``
    Specifies the connection to a SQLite database.
``sql``
    Specifies a SQL statement to execute.

We will write a PBBT extension implementing these test types.

Create a file ``sql.py`` with the following content::

    from pbbt import Test, Field, BaseCase, MatchCase, listof
    import sqlite3, traceback, csv, StringIO

    @Test
    class ConnectCase(BaseCase):

        class Input:
            connect = Field(str)

        def check(self):
            self.state['connect'] = None
            try:
                self.state['connect'] = sqlite3.connect(self.input.connect)
            except:
                self.ui.literal(traceback.format_exc())
                self.ui.warning("exception occurred while"
                                " connecting to the database")
                self.ctl.failed()
            else:
                self.ctl.passed()

    @Test
    class SQLCase(MatchCase):

        class Input:
            sql = Field(str)

        class Output:
            sql = Field(str)
            rows = Field(listof(listof(object)))

        def render(self, output):
            stream = StringIO.StringIO()
            writer = csv.writer(stream, lineterminator='\n')
            writer.writerows(output.rows)
            return stream.getvalue()

        def run(self):
            connection = self.state.get('connect')
            if not connection:
                self.ui.warning("database connection is not defined")
                return
            rows = []
            try:
                cursor = connection.cursor()
                cursor.execute(self.input.sql)
                for row in cursor.fetchall():
                    rows.append(list(row))
            except:
                self.ui.literal(traceback.format_exc())
                self.ui.warning("exception occurred while"
                                " executing a SQL query")
                connection.rollback()
                new_output = None
            else:
                connection.commit()
                new_output = self.Output(sql=self.input.sql, rows=rows)
            return new_output

To use this extension, add parameter ``-E sql.py`` to all PBBT
invocations.  For example::

    $ pbbt -E sql.py input.yaml output.yaml --train

Now we will explain the content of ``sql.py`` line by line.

The first line imports some classes and decorators we will use::

    from pbbt import Test, Field, BaseCase, MatchCase

To register a test type, use ``@Test`` decorator.  Here is a most
general template::

    @Test
    class CustomCase(object):

        class Input:
            some_field = Field(...)
            [...]

        class Output:
            some_field = Field(...)
            [...]

        def __init__(self, ctl, input, output):
            self.ctl = ctl
            self.input = input
            self.output = output

        def __call__(self):
            [...]
            return new_output

The argument of the decorator must be a class that adheres the following
rules:

* The structure of input and output records is described with nested
  classes ``Input`` and ``Output``.  Record fields are specified using
  ``Field`` descriptor.

* To create a test case, the test harness makes an instance of the class.
  The class constructor accepts three arguments:

  ``ctl``
      Test harness controller.  It is used for user interaction,
      reporting test success or failure, and as a storage for
      conditional variables.
  ``input``
      The input record.
  ``output``
      The expected output record or ``None``.

* The test case is executed by calling its ``__call__()`` method.  This
  method must run the test case, generate a new output record, and compare
  it with the given expected output record.

  If the expected and actual output record do not coincide:

  * In the *check* mode, the method must report a failure.
  * In the *train* mode, the method may ask the user for permission to
    update expected output.  If expected output is to be updated, the
    method should return the new output record.

PBBT also provides two mixin classes: ``BaseCase`` and ``MatchCase``.
These classes implement most of the necessary functionality for common
types of tests.

Let's review ``connect`` test type, which is implemented by
``ConnectCase`` class::

    @Test
    class ConnectCase(BaseCase):

        class Input:
            connect = Field(str)

        def check(self):
            [...]

``ConnectCase`` is inherited from ``BaseCase``, which is suitable for
test which produce no output data and are executed for their side
effects.  The nested ``Input`` class definition is used to declare the
fields of the input record.  In this case, the input record has just one
text field ``connect``, which contains the name of the database.

Test types inherited from ``BaseCase`` must override abstract method
``check()``::

    import sqlite3, traceback
    [...]

    @Test
    class ConnectCase(BaseCase):
        [...]

        def check(self):
            self.state['connect'] = None
            try:
                self.state['connect'] = sqlite3.connect(self.input.connect)
            except:
                self.ui.literal(traceback.format_exc())
                self.ui.warning("exception occurred while"
                                " connecting to the database")
                self.ctl.failed()
            else:
                self.ctl.passed()

This code attempts to create a new database connection and store it as a
conditional variable ``connect``.  If the attempt fails, it calls
``ui.literal()`` to display the exception traceback and ``ctl.failed()``
to report test failure.  Otherwise, ``ctl.passed()`` is called to
indicate that the test succeeded.

Next, let's review ``sql`` test type::

    @Test
    class SQLCase(MatchCase):

        class Input:
            sql = Field(str)

        class Output:
            sql = Field(str)
            rows = Field(listof(listof(object)))

        def run(self):
            [...]

        def render(self, output):
            [...]

This test type has both input and output records, which are described
with ``Input`` and ``Output`` nested classes.  The input record contains
one field ``sql``, a SQL query to execute.  The output record contains
two fields: ``sql`` and ``rows``.  Field ``sql`` contains the same SQL
query and is used for matching the output record with the complementary
input record.  Field ``rows`` contains a list of output rows generated
by the SQL query.

``SQLCase`` is inherited from ``MatchCase``, which is a mixin class
for test types that produce text output.  Test types inherited from
``MatchCase`` must override two methods:

``run()``
    Executes the test case and returns the produced output record.
``render(output)``
    Convert an output record to printable form.

In ``SQLCase``, ``render()`` is implemented by converting output rows to
CSV format::

    import csv, StringIO
    [...]

    @Test
    class SQLCase(MatchCase):
        [...]

        def render(self, output):
            stream = StringIO.StringIO()
            writer = csv.writer(stream, lineterminator='\n')
            writer.writerows(output.rows)
            return stream.getvalue()

Method ``run()`` is implemented as follows::

    @Test
    class SQLCase(MatchCase):
        [...]

        def run(self):
            connection = self.state.get('connect')
            if not connection:
                self.ui.warning("database connection is not defined")
                return
            rows = []
            try:
                cursor = connection.cursor()
                cursor.execute(self.input.sql)
                for row in cursor.fetchall():
                    rows.append(list(row))
            except:
                self.ui.literal(traceback.format_exc())
                self.ui.warning("exception occurred while"
                                " executing a SQL query")
                connection.rollback()
                new_output = None
            else:
                connection.commit()
                new_output = self.Output(sql=self.input.sql, rows=rows)
            return new_output


Command-line Interface
======================

Usage::

    pbbt [<options>] INPUT [OUTPUT]

Here, ``INPUT`` and ``OUTPUT`` are files which contain input and output
test data respectively.

The following options are available:

``-h``, ``--help``
    Display usage information and exit.

``-q``, ``--quiet``
    Show only warnings and errors.

``-T``, ``--train``
    Run tests in the training mode.

``-P``, ``--purge``
    Purge stale output data.

``-M N``, ``--max-errors N``
    Halt after ``N`` tests failed; ``0`` means "never".

``-D VAR``, ``-D VAR=VALUE``, ``--define VAR``, ``--define VAR=VALUE``
    Set a conditional variable.

``-E FILE``, ``-E MODULE``, ``--extend FILE``, ``--extend MODULE``
    Load a PBBT extension from a file or a Python module.

``-S ID``, ``--suite ID``
    Run a specific test suite.

PBBT can also read configuration from the following files:

``setup.cfg``
    This file is in INI format with PBBT settings defined in section
    ``[pbbt]``.  The following parameters are recognized: ``extend``,
    ``input``, ``output``, ``define``, ``suite``, ``train``, ``purge``,
    ``max_errors``, ``quiet``.

``pbbt.yaml``
    This file must be a YAML file with the following keys: ``extend``,
    ``input``, ``output``, ``define``, ``suite``, ``train``, ``purge``,
    ``max-errors``, ``quiet``.

PBBT can also be executed as a Distutils command::

    python setup.py pbbt

In this case, PBBT configuration could be specified in ``setup.cfg``
or via command-line parameters.


API Reference
=============

``pbbt.maybe(T)``
    Pseudo-type for ``isinstance(X, ...)``: checks if ``X`` is an
    instance of ``T`` or equal to ``None``.

``pbbt.oneof(T1, T2, ...)``
    Pseudo-type for ``isinstance(X, ...)``: checks if ``X`` is an
    instance of ``T1`` or an instance of ``T2``, etc.

``pbbt.choiceof(values)``
    Pseudo-type for ``isinstance(X, ...)``: checks if ``X`` is equal to
    one of the given values.

``pbbt.listof(T, length=None)``
    Pseudo-type for ``isinstance(X, ...)``: checks if ``X`` is a list of
    elements of ``T``.

``pbbt.tupleof(T1, T2, ...)``
    Pseudo-type for ``isinstance(X, ...)``: checks if ``X`` is a tuple
    with fields of types ``T1``, ``T2``, etc.

``pbbt.dictof(T1, T2)``
    Pseudo-type for ``isinstance(X, ...)``: checks if ``X`` is a
    dictionary with keys of type ``T1`` and values of type ``T2``.

``pbbt.raises(E)``
    Use with ``with`` clause to verify that the nested block raises an
    exception of the given type.

``pbbt.raises(E, fn, *args, **kwds)``
    Verifies that the function call ``fn(*args, **kwds)`` raises an
    exception of the given type.

``pbbt.Test(CaseType)``
    Registers the given class as a test type.

``pbbt.Field(check=None, default=REQUIRED, order=None, hint=None)``
    Describes a field of an input or an output record.

    ``check``
        The type of the field value.

    ``default``
        Default value if the field is missing.  If not set, the
        field is mandatory.

    ``order``
        If set, allows you to override the default field order.

    ``hint``
        Short description of the field.

``pbbt.Record(*p_fields, **kv_fields)``
    Base class for all input and output records.

    The ``Test`` decorator converts nested ``Input`` and ``Output``
    classes to ``Record`` subclasses.

    The following methods could be used or overridden:

    ``classmethod __recognizes__(keys)``
        Checks if the set of keys is compatible with the record type.

        The default implementation checks if the set of keys contains
        all mandatory record fields.

    ``classmethod __load__(mapping)``
        Generates a record instance from a mapping of record keys and
        values.

    ``__dump__()``
        Generates a list of field keys and values.

    ``__complements__(other)``
        Checks if two records are complementary input and output records
        for the same test case.

    ``__clone__(**kv_fields)``
        Makes a copy of the record with new values for the given fields.

    ``__str__()``
        Generates a printable representation.

``pbbt.Control(...)``
    Test harness.

    The test harness object is passed to test cases as the first
    argument of the constructor.  The following methods and attributes
    could be used by test case objects.

    Attributes:

    ``ui``
        Provides user interaction services.

    ``training``
        If set, the harness is in training mode.

    ``purging``
        If set, the harness is in purging mode.

    ``quiet``
        If set, only warnings and errors are displayed.

    ``halted``
        If set, the test process has been halted.

    ``state``
        Conditional variables.

    ``selection``
        Selected suites.

    Methods:

    ``passed(text=None)``
        Attests that the current test case has passed.

    ``failed(text=None)``
        Attests that the current test case has failed.

    ``updated(text=None)``
        Attests that output data for the current test case has been
        updated.

    ``halt(text=None)``
        Halts testing process.

    ``load_input(path)``
        Loads input test data from the given file.

    ``load_output(path)``
        Loads output test data from the given file.

    ``dump_output(path, data)``
        Saves output test data to the given file.

    ``run(case)``
        Executes a test case.

    ``__call__(input_path, output_path)``
        Runs testing process with the given input and output.

``pbbt.locate(record)``
    Finds the location of the given record.

``pbbt.Location(filename, line)``
    Position of an input or output record in the YAML document.

``pbbt.run(input_path, output_path=None, **configuration)``
    Loads test data from the given files and runs the tests.

    Configuration:

    ``ui``
        User interaction controller.
    ``variables``
        Predefined conditional variables.
    ``targets``
        Selected suites.
    ``training``
        Set the harness into training mode.
    ``purging``
        Purge stale output data.
    ``max_errors``
        Maximum permitted number of failures before the harness halts.
    ``quiet``
        Display only warnings and errors.

``pbbt.main()``
    Implements the ``pbbt`` command-line utility.

``pbbt.BaseCase``
    Template class suitable for most test types.

    Subclasses need to override the following methods:

    ``check()``
        Runs the test case in check mode.

    ``train()``
        Runs the test case in train mode.  The default implementation
        simply calls ``check()``.

``pbbt.MatchCase``
    Template class for test types which produce output.

    Subclasses need to override the following methods:

    ``run()``
        Executes the case; returns produced output.

    ``render(output)``
        Converts output record to text.

``pbbt.UI``
    Abstract class for user interaction services.

    Methods:

    ``part()``
        Starts a new section.

    ``section()``
        Starts a subsection.

    ``header(text)``
        Shows a section header.

    ``notice(text)``
        Shows a notice.

    ``warning(text)``
        Shows a warning.

    ``error(text)``
        Shows an error.

    ``literal(text)``
        Shows a literal text.

    ``choice(text, *choices)``
        Asks a single-choice question.

``pbbt.ConsoleUI(stdin=None, stdout=None, stderr=None)``
    Implements ``UI`` for console input/output.

``pbbt.SilentUI(backend)``
    Implements ``UI`` for use with ``--quiet`` option.


.. _YAML: http://yaml.org/
.. _Prometheus Research, LLC: http://prometheusresearch.com/
.. _pip: http://pip-installer.org/
.. _Python Package Index: http://pypi.python.org/pypi/pbbt
.. _JSON: http://json.org/

.. vim: set spell spelllang=en textwidth=72: