/setuptools/tests/doctest.py

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# Module doctest.
# Released to the public domain 16-Jan-2001, by Tim Peters (tim@python.org).
# Major enhancements and refactoring by:
#     Jim Fulton
#     Edward Loper

# Provided as-is; use at your own risk; no warranty; no promises; enjoy!

try:
    basestring
except NameError:
    basestring = str,unicode

try:
    enumerate
except NameError:
    def enumerate(seq):
        return zip(range(len(seq)),seq)

r"""Module doctest -- a framework for running examples in docstrings.

In simplest use, end each module M to be tested with:

def _test():
    import doctest
    doctest.testmod()

if __name__ == "__main__":
    _test()

Then running the module as a script will cause the examples in the
docstrings to get executed and verified:

python M.py

This won't display anything unless an example fails, in which case the
failing example(s) and the cause(s) of the failure(s) are printed to stdout
(why not stderr? because stderr is a lame hack <0.2 wink>), and the final
line of output is "Test failed.".

Run it with the -v switch instead:

python M.py -v

and a detailed report of all examples tried is printed to stdout, along
with assorted summaries at the end.

You can force verbose mode by passing "verbose=True" to testmod, or prohibit
it by passing "verbose=False".  In either of those cases, sys.argv is not
examined by testmod.

There are a variety of other ways to run doctests, including integration
with the unittest framework, and support for running non-Python text
files containing doctests.  There are also many ways to override parts
of doctest's default behaviors.  See the Library Reference Manual for
details.
"""

__docformat__ = 'reStructuredText en'

__all__ = [
    # 0, Option Flags
    'register_optionflag',
    'DONT_ACCEPT_TRUE_FOR_1',
    'DONT_ACCEPT_BLANKLINE',
    'NORMALIZE_WHITESPACE',
    'ELLIPSIS',
    'IGNORE_EXCEPTION_DETAIL',
    'COMPARISON_FLAGS',
    'REPORT_UDIFF',
    'REPORT_CDIFF',
    'REPORT_NDIFF',
    'REPORT_ONLY_FIRST_FAILURE',
    'REPORTING_FLAGS',
    # 1. Utility Functions
    'is_private',
    # 2. Example & DocTest
    'Example',
    'DocTest',
    # 3. Doctest Parser
    'DocTestParser',
    # 4. Doctest Finder
    'DocTestFinder',
    # 5. Doctest Runner
    'DocTestRunner',
    'OutputChecker',
    'DocTestFailure',
    'UnexpectedException',
    'DebugRunner',
    # 6. Test Functions
    'testmod',
    'testfile',
    'run_docstring_examples',
    # 7. Tester
    'Tester',
    # 8. Unittest Support
    'DocTestSuite',
    'DocFileSuite',
    'set_unittest_reportflags',
    # 9. Debugging Support
    'script_from_examples',
    'testsource',
    'debug_src',
    'debug',
]

import __future__

import sys, traceback, inspect, linecache, os, re, types
import unittest, difflib, pdb, tempfile
import warnings
from StringIO import StringIO

# Don't whine about the deprecated is_private function in this
# module's tests.
warnings.filterwarnings("ignore", "is_private", DeprecationWarning,
                        __name__, 0)

# There are 4 basic classes:
#  - Example: a <source, want> pair, plus an intra-docstring line number.
#  - DocTest: a collection of examples, parsed from a docstring, plus
#    info about where the docstring came from (name, filename, lineno).
#  - DocTestFinder: extracts DocTests from a given object's docstring and
#    its contained objects' docstrings.
#  - DocTestRunner: runs DocTest cases, and accumulates statistics.
#
# So the basic picture is:
#
#                             list of:
# +------+                   +---------+                   +-------+
# |object| --DocTestFinder-> | DocTest | --DocTestRunner-> |results|
# +------+                   +---------+                   +-------+
#                            | Example |
#                            |   ...   |
#                            | Example |
#                            +---------+

# Option constants.

OPTIONFLAGS_BY_NAME = {}
def register_optionflag(name):
    flag = 1 << len(OPTIONFLAGS_BY_NAME)
    OPTIONFLAGS_BY_NAME[name] = flag
    return flag

DONT_ACCEPT_TRUE_FOR_1 = register_optionflag('DONT_ACCEPT_TRUE_FOR_1')
DONT_ACCEPT_BLANKLINE = register_optionflag('DONT_ACCEPT_BLANKLINE')
NORMALIZE_WHITESPACE = register_optionflag('NORMALIZE_WHITESPACE')
ELLIPSIS = register_optionflag('ELLIPSIS')
IGNORE_EXCEPTION_DETAIL = register_optionflag('IGNORE_EXCEPTION_DETAIL')

COMPARISON_FLAGS = (DONT_ACCEPT_TRUE_FOR_1 |
                    DONT_ACCEPT_BLANKLINE |
                    NORMALIZE_WHITESPACE |
                    ELLIPSIS |
                    IGNORE_EXCEPTION_DETAIL)

REPORT_UDIFF = register_optionflag('REPORT_UDIFF')
REPORT_CDIFF = register_optionflag('REPORT_CDIFF')
REPORT_NDIFF = register_optionflag('REPORT_NDIFF')
REPORT_ONLY_FIRST_FAILURE = register_optionflag('REPORT_ONLY_FIRST_FAILURE')

REPORTING_FLAGS = (REPORT_UDIFF |
                   REPORT_CDIFF |
                   REPORT_NDIFF |
                   REPORT_ONLY_FIRST_FAILURE)

# Special string markers for use in `want` strings:
BLANKLINE_MARKER = '<BLANKLINE>'
ELLIPSIS_MARKER = '...'

######################################################################
## Table of Contents
######################################################################
#  1. Utility Functions
#  2. Example & DocTest -- store test cases
#  3. DocTest Parser -- extracts examples from strings
#  4. DocTest Finder -- extracts test cases from objects
#  5. DocTest Runner -- runs test cases
#  6. Test Functions -- convenient wrappers for testing
#  7. Tester Class -- for backwards compatibility
#  8. Unittest Support
#  9. Debugging Support
# 10. Example Usage

######################################################################
## 1. Utility Functions
######################################################################

def is_private(prefix, base):
    """prefix, base -> true iff name prefix + "." + base is "private".

    Prefix may be an empty string, and base does not contain a period.
    Prefix is ignored (although functions you write conforming to this
    protocol may make use of it).
    Return true iff base begins with an (at least one) underscore, but
    does not both begin and end with (at least) two underscores.

    >>> is_private("a.b", "my_func")
    False
    >>> is_private("____", "_my_func")
    True
    >>> is_private("someclass", "__init__")
    False
    >>> is_private("sometypo", "__init_")
    True
    >>> is_private("x.y.z", "_")
    True
    >>> is_private("_x.y.z", "__")
    False
    >>> is_private("", "")  # senseless but consistent
    False
    """
    warnings.warn("is_private is deprecated; it wasn't useful; "
                  "examine DocTestFinder.find() lists instead",
                  DeprecationWarning, stacklevel=2)
    return base[:1] == "_" and not base[:2] == "__" == base[-2:]

def _extract_future_flags(globs):
    """
    Return the compiler-flags associated with the future features that
    have been imported into the given namespace (globs).
    """
    flags = 0
    for fname in __future__.all_feature_names:
        feature = globs.get(fname, None)
        if feature is getattr(__future__, fname):
            flags |= feature.compiler_flag
    return flags

def _normalize_module(module, depth=2):
    """
    Return the module specified by `module`.  In particular:
      - If `module` is a module, then return module.
      - If `module` is a string, then import and return the
        module with that name.
      - If `module` is None, then return the calling module.
        The calling module is assumed to be the module of
        the stack frame at the given depth in the call stack.
    """
    if inspect.ismodule(module):
        return module
    elif isinstance(module, (str, unicode)):
        return __import__(module, globals(), locals(), ["*"])
    elif module is None:
        return sys.modules[sys._getframe(depth).f_globals['__name__']]
    else:
        raise TypeError("Expected a module, string, or None")

def _indent(s, indent=4):
    """
    Add the given number of space characters to the beginning every
    non-blank line in `s`, and return the result.
    """
    # This regexp matches the start of non-blank lines:
    return re.sub('(?m)^(?!$)', indent*' ', s)

def _exception_traceback(exc_info):
    """
    Return a string containing a traceback message for the given
    exc_info tuple (as returned by sys.exc_info()).
    """
    # Get a traceback message.
    excout = StringIO()
    exc_type, exc_val, exc_tb = exc_info
    traceback.print_exception(exc_type, exc_val, exc_tb, file=excout)
    return excout.getvalue()

# Override some StringIO methods.
class _SpoofOut(StringIO):
    def getvalue(self):
        result = StringIO.getvalue(self)
        # If anything at all was written, make sure there's a trailing
        # newline.  There's no way for the expected output to indicate
        # that a trailing newline is missing.
        if result and not result.endswith("\n"):
            result += "\n"
        # Prevent softspace from screwing up the next test case, in
        # case they used print with a trailing comma in an example.
        if hasattr(self, "softspace"):
            del self.softspace
        return result

    def truncate(self,   size=None):
        StringIO.truncate(self, size)
        if hasattr(self, "softspace"):
            del self.softspace

# Worst-case linear-time ellipsis matching.
def _ellipsis_match(want, got):
    """
    Essentially the only subtle case:
    >>> _ellipsis_match('aa...aa', 'aaa')
    False
    """
    if want.find(ELLIPSIS_MARKER)==-1:
        return want == got

    # Find "the real" strings.
    ws = want.split(ELLIPSIS_MARKER)
    assert len(ws) >= 2

    # Deal with exact matches possibly needed at one or both ends.
    startpos, endpos = 0, len(got)
    w = ws[0]
    if w:   # starts with exact match
        if got.startswith(w):
            startpos = len(w)
            del ws[0]
        else:
            return False
    w = ws[-1]
    if w:   # ends with exact match
        if got.endswith(w):
            endpos -= len(w)
            del ws[-1]
        else:
            return False

    if startpos > endpos:
        # Exact end matches required more characters than we have, as in
        # _ellipsis_match('aa...aa', 'aaa')
        return False

    # For the rest, we only need to find the leftmost non-overlapping
    # match for each piece.  If there's no overall match that way alone,
    # there's no overall match period.
    for w in ws:
        # w may be '' at times, if there are consecutive ellipses, or
        # due to an ellipsis at the start or end of `want`.  That's OK.
        # Search for an empty string succeeds, and doesn't change startpos.
        startpos = got.find(w, startpos, endpos)
        if startpos < 0:
            return False
        startpos += len(w)

    return True

def _comment_line(line):
    "Return a commented form of the given line"
    line = line.rstrip()
    if line:
        return '# '+line
    else:
        return '#'

class _OutputRedirectingPdb(pdb.Pdb):
    """
    A specialized version of the python debugger that redirects stdout
    to a given stream when interacting with the user.  Stdout is *not*
    redirected when traced code is executed.
    """
    def __init__(self, out):
        self.__out = out
        pdb.Pdb.__init__(self)

    def trace_dispatch(self, *args):
        # Redirect stdout to the given stream.
        save_stdout = sys.stdout
        sys.stdout = self.__out
        # Call Pdb's trace dispatch method.
        try:
            return pdb.Pdb.trace_dispatch(self, *args)
        finally:
            sys.stdout = save_stdout

# [XX] Normalize with respect to os.path.pardir?
def _module_relative_path(module, path):
    if not inspect.ismodule(module):
        raise TypeError, 'Expected a module: %r' % module
    if path.startswith('/'):
        raise ValueError, 'Module-relative files may not have absolute paths'

    # Find the base directory for the path.
    if hasattr(module, '__file__'):
        # A normal module/package
        basedir = os.path.split(module.__file__)[0]
    elif module.__name__ == '__main__':
        # An interactive session.
        if len(sys.argv)>0 and sys.argv[0] != '':
            basedir = os.path.split(sys.argv[0])[0]
        else:
            basedir = os.curdir
    else:
        # A module w/o __file__ (this includes builtins)
        raise ValueError("Can't resolve paths relative to the module " +
                         module + " (it has no __file__)")

    # Combine the base directory and the path.
    return os.path.join(basedir, *(path.split('/')))

######################################################################
## 2. Example & DocTest
######################################################################
## - An "example" is a <source, want> pair, where "source" is a
##   fragment of source code, and "want" is the expected output for
##   "source."  The Example class also includes information about
##   where the example was extracted from.
##
## - A "doctest" is a collection of examples, typically extracted from
##   a string (such as an object's docstring).  The DocTest class also
##   includes information about where the string was extracted from.

class Example:
    """
    A single doctest example, consisting of source code and expected
    output.  `Example` defines the following attributes:

      - source: A single Python statement, always ending with a newline.
        The constructor adds a newline if needed.

      - want: The expected output from running the source code (either
        from stdout, or a traceback in case of exception).  `want` ends
        with a newline unless it's empty, in which case it's an empty
        string.  The constructor adds a newline if needed.

      - exc_msg: The exception message generated by the example, if
        the example is expected to generate an exception; or `None` if
        it is not expected to generate an exception.  This exception
        message is compared against the return value of
        `traceback.format_exception_only()`.  `exc_msg` ends with a
        newline unless it's `None`.  The constructor adds a newline
        if needed.

      - lineno: The line number within the DocTest string containing
        this Example where the Example begins.  This line number is
        zero-based, with respect to the beginning of the DocTest.

      - indent: The example's indentation in the DocTest string.
        I.e., the number of space characters that preceed the
        example's first prompt.

      - options: A dictionary mapping from option flags to True or
        False, which is used to override default options for this
        example.  Any option flags not contained in this dictionary
        are left at their default value (as specified by the
        DocTestRunner's optionflags).  By default, no options are set.
    """
    def __init__(self, source, want, exc_msg=None, lineno=0, indent=0,
                 options=None):
        # Normalize inputs.
        if not source.endswith('\n'):
            source += '\n'
        if want and not want.endswith('\n'):
            want += '\n'
        if exc_msg is not None and not exc_msg.endswith('\n'):
            exc_msg += '\n'
        # Store properties.
        self.source = source
        self.want = want
        self.lineno = lineno
        self.indent = indent
        if options is None: options = {}
        self.options = options
        self.exc_msg = exc_msg

class DocTest:
    """
    A collection of doctest examples that should be run in a single
    namespace.  Each `DocTest` defines the following attributes:

      - examples: the list of examples.

      - globs: The namespace (aka globals) that the examples should
        be run in.

      - name: A name identifying the DocTest (typically, the name of
        the object whose docstring this DocTest was extracted from).

      - filename: The name of the file that this DocTest was extracted
        from, or `None` if the filename is unknown.

      - lineno: The line number within filename where this DocTest
        begins, or `None` if the line number is unavailable.  This
        line number is zero-based, with respect to the beginning of
        the file.

      - docstring: The string that the examples were extracted from,
        or `None` if the string is unavailable.
    """
    def __init__(self, examples, globs, name, filename, lineno, docstring):
        """
        Create a new DocTest containing the given examples.  The
        DocTest's globals are initialized with a copy of `globs`.
        """
        assert not isinstance(examples, basestring), \
               "DocTest no longer accepts str; use DocTestParser instead"
        self.examples = examples
        self.docstring = docstring
        self.globs = globs.copy()
        self.name = name
        self.filename = filename
        self.lineno = lineno

    def __repr__(self):
        if len(self.examples) == 0:
            examples = 'no examples'
        elif len(self.examples) == 1:
            examples = '1 example'
        else:
            examples = '%d examples' % len(self.examples)
        return ('<DocTest %s from %s:%s (%s)>' %
                (self.name, self.filename, self.lineno, examples))


    # This lets us sort tests by name:
    def __cmp__(self, other):
        if not isinstance(other, DocTest):
            return -1
        return cmp((self.name, self.filename, self.lineno, id(self)),
                   (other.name, other.filename, other.lineno, id(other)))

######################################################################
## 3. DocTestParser
######################################################################

class DocTestParser:
    """
    A class used to parse strings containing doctest examples.
    """
    # This regular expression is used to find doctest examples in a
    # string.  It defines three groups: `source` is the source code
    # (including leading indentation and prompts); `indent` is the
    # indentation of the first (PS1) line of the source code; and
    # `want` is the expected output (including leading indentation).
    _EXAMPLE_RE = re.compile(r'''
        # Source consists of a PS1 line followed by zero or more PS2 lines.
        (?P<source>
            (?:^(?P<indent> [ ]*) >>>    .*)    # PS1 line
            (?:\n           [ ]*  \.\.\. .*)*)  # PS2 lines
        \n?
        # Want consists of any non-blank lines that do not start with PS1.
        (?P<want> (?:(?![ ]*$)    # Not a blank line
                     (?![ ]*>>>)  # Not a line starting with PS1
                     .*$\n?       # But any other line
                  )*)
        ''', re.MULTILINE | re.VERBOSE)

    # A regular expression for handling `want` strings that contain
    # expected exceptions.  It divides `want` into three pieces:
    #    - the traceback header line (`hdr`)
    #    - the traceback stack (`stack`)
    #    - the exception message (`msg`), as generated by
    #      traceback.format_exception_only()
    # `msg` may have multiple lines.  We assume/require that the
    # exception message is the first non-indented line starting with a word
    # character following the traceback header line.
    _EXCEPTION_RE = re.compile(r"""
        # Grab the traceback header.  Different versions of Python have
        # said different things on the first traceback line.
        ^(?P<hdr> Traceback\ \(
            (?: most\ recent\ call\ last
            |   innermost\ last
            ) \) :
        )
        \s* $                # toss trailing whitespace on the header.
        (?P<stack> .*?)      # don't blink: absorb stuff until...
        ^ (?P<msg> \w+ .*)   #     a line *starts* with alphanum.
        """, re.VERBOSE | re.MULTILINE | re.DOTALL)

    # A callable returning a true value iff its argument is a blank line
    # or contains a single comment.
    _IS_BLANK_OR_COMMENT = re.compile(r'^[ ]*(#.*)?$').match

    def parse(self, string, name='<string>'):
        """
        Divide the given string into examples and intervening text,
        and return them as a list of alternating Examples and strings.
        Line numbers for the Examples are 0-based.  The optional
        argument `name` is a name identifying this string, and is only
        used for error messages.
        """
        string = string.expandtabs()
        # If all lines begin with the same indentation, then strip it.
        min_indent = self._min_indent(string)
        if min_indent > 0:
            string = '\n'.join([l[min_indent:] for l in string.split('\n')])

        output = []
        charno, lineno = 0, 0
        # Find all doctest examples in the string:
        for m in self._EXAMPLE_RE.finditer(string):
            # Add the pre-example text to `output`.
            output.append(string[charno:m.start()])
            # Update lineno (lines before this example)
            lineno += string.count('\n', charno, m.start())
            # Extract info from the regexp match.
            (source, options, want, exc_msg) = \
                     self._parse_example(m, name, lineno)
            # Create an Example, and add it to the list.
            if not self._IS_BLANK_OR_COMMENT(source):
                output.append( Example(source, want, exc_msg,
                                    lineno=lineno,
                                    indent=min_indent+len(m.group('indent')),
                                    options=options) )
            # Update lineno (lines inside this example)
            lineno += string.count('\n', m.start(), m.end())
            # Update charno.
            charno = m.end()
        # Add any remaining post-example text to `output`.
        output.append(string[charno:])
        return output

    def get_doctest(self, string, globs, name, filename, lineno):
        """
        Extract all doctest examples from the given string, and
        collect them into a `DocTest` object.

        `globs`, `name`, `filename`, and `lineno` are attributes for
        the new `DocTest` object.  See the documentation for `DocTest`
        for more information.
        """
        return DocTest(self.get_examples(string, name), globs,
                       name, filename, lineno, string)

    def get_examples(self, string, name='<string>'):
        """
        Extract all doctest examples from the given string, and return
        them as a list of `Example` objects.  Line numbers are
        0-based, because it's most common in doctests that nothing
        interesting appears on the same line as opening triple-quote,
        and so the first interesting line is called \"line 1\" then.

        The optional argument `name` is a name identifying this
        string, and is only used for error messages.
        """
        return [x for x in self.parse(string, name)
                if isinstance(x, Example)]

    def _parse_example(self, m, name, lineno):
        """
        Given a regular expression match from `_EXAMPLE_RE` (`m`),
        return a pair `(source, want)`, where `source` is the matched
        example's source code (with prompts and indentation stripped);
        and `want` is the example's expected output (with indentation
        stripped).

        `name` is the string's name, and `lineno` is the line number
        where the example starts; both are used for error messages.
        """
        # Get the example's indentation level.
        indent = len(m.group('indent'))

        # Divide source into lines; check that they're properly
        # indented; and then strip their indentation & prompts.
        source_lines = m.group('source').split('\n')
        self._check_prompt_blank(source_lines, indent, name, lineno)
        self._check_prefix(source_lines[1:], ' '*indent + '.', name, lineno)
        source = '\n'.join([sl[indent+4:] for sl in source_lines])

        # Divide want into lines; check that it's properly indented; and
        # then strip the indentation.  Spaces before the last newline should
        # be preserved, so plain rstrip() isn't good enough.
        want = m.group('want')
        want_lines = want.split('\n')
        if len(want_lines) > 1 and re.match(r' *$', want_lines[-1]):
            del want_lines[-1]  # forget final newline & spaces after it
        self._check_prefix(want_lines, ' '*indent, name,
                           lineno + len(source_lines))
        want = '\n'.join([wl[indent:] for wl in want_lines])

        # If `want` contains a traceback message, then extract it.
        m = self._EXCEPTION_RE.match(want)
        if m:
            exc_msg = m.group('msg')
        else:
            exc_msg = None

        # Extract options from the source.
        options = self._find_options(source, name, lineno)

        return source, options, want, exc_msg

    # This regular expression looks for option directives in the
    # source code of an example.  Option directives are comments
    # starting with "doctest:".  Warning: this may give false
    # positives for string-literals that contain the string
    # "#doctest:".  Eliminating these false positives would require
    # actually parsing the string; but we limit them by ignoring any
    # line containing "#doctest:" that is *followed* by a quote mark.
    _OPTION_DIRECTIVE_RE = re.compile(r'#\s*doctest:\s*([^\n\'"]*)$',
                                      re.MULTILINE)

    def _find_options(self, source, name, lineno):
        """
        Return a dictionary containing option overrides extracted from
        option directives in the given source string.

        `name` is the string's name, and `lineno` is the line number
        where the example starts; both are used for error messages.
        """
        options = {}
        # (note: with the current regexp, this will match at most once:)
        for m in self._OPTION_DIRECTIVE_RE.finditer(source):
            option_strings = m.group(1).replace(',', ' ').split()
            for option in option_strings:
                if (option[0] not in '+-' or
                    option[1:] not in OPTIONFLAGS_BY_NAME):
                    raise ValueError('line %r of the doctest for %s '
                                     'has an invalid option: %r' %
                                     (lineno+1, name, option))
                flag = OPTIONFLAGS_BY_NAME[option[1:]]
                options[flag] = (option[0] == '+')
        if options and self._IS_BLANK_OR_COMMENT(source):
            raise ValueError('line %r of the doctest for %s has an option '
                             'directive on a line with no example: %r' %
                             (lineno, name, source))
        return options

    # This regular expression finds the indentation of every non-blank
    # line in a string.
    _INDENT_RE = re.compile('^([ ]*)(?=\S)', re.MULTILINE)

    def _min_indent(self, s):
        "Return the minimum indentation of any non-blank line in `s`"
        indents = [len(indent) for indent in self._INDENT_RE.findall(s)]
        if len(indents) > 0:
            return min(indents)
        else:
            return 0

    def _check_prompt_blank(self, lines, indent, name, lineno):
        """
        Given the lines of a source string (including prompts and
        leading indentation), check to make sure that every prompt is
        followed by a space character.  If any line is not followed by
        a space character, then raise ValueError.
        """
        for i, line in enumerate(lines):
            if len(line) >= indent+4 and line[indent+3] != ' ':
                raise ValueError('line %r of the docstring for %s '
                                 'lacks blank after %s: %r' %
                                 (lineno+i+1, name,
                                  line[indent:indent+3], line))

    def _check_prefix(self, lines, prefix, name, lineno):
        """
        Check that every line in the given list starts with the given
        prefix; if any line does not, then raise a ValueError.
        """
        for i, line in enumerate(lines):
            if line and not line.startswith(prefix):
                raise ValueError('line %r of the docstring for %s has '
                                 'inconsistent leading whitespace: %r' %
                                 (lineno+i+1, name, line))


######################################################################
## 4. DocTest Finder
######################################################################

class DocTestFinder:
    """
    A class used to extract the DocTests that are relevant to a given
    object, from its docstring and the docstrings of its contained
    objects.  Doctests can currently be extracted from the following
    object types: modules, functions, classes, methods, staticmethods,
    classmethods, and properties.
    """

    def __init__(self, verbose=False, parser=DocTestParser(),
                 recurse=True, _namefilter=None, exclude_empty=True):
        """
        Create a new doctest finder.

        The optional argument `parser` specifies a class or
        function that should be used to create new DocTest objects (or
        objects that implement the same interface as DocTest).  The
        signature for this factory function should match the signature
        of the DocTest constructor.

        If the optional argument `recurse` is false, then `find` will
        only examine the given object, and not any contained objects.

        If the optional argument `exclude_empty` is false, then `find`
        will include tests for objects with empty docstrings.
        """
        self._parser = parser
        self._verbose = verbose
        self._recurse = recurse
        self._exclude_empty = exclude_empty
        # _namefilter is undocumented, and exists only for temporary backward-
        # compatibility support of testmod's deprecated isprivate mess.
        self._namefilter = _namefilter

    def find(self, obj, name=None, module=None, globs=None,
             extraglobs=None):
        """
        Return a list of the DocTests that are defined by the given
        object's docstring, or by any of its contained objects'
        docstrings.

        The optional parameter `module` is the module that contains
        the given object.  If the module is not specified or is None, then
        the test finder will attempt to automatically determine the
        correct module.  The object's module is used:

            - As a default namespace, if `globs` is not specified.
            - To prevent the DocTestFinder from extracting DocTests
              from objects that are imported from other modules.
            - To find the name of the file containing the object.
            - To help find the line number of the object within its
              file.

        Contained objects whose module does not match `module` are ignored.

        If `module` is False, no attempt to find the module will be made.
        This is obscure, of use mostly in tests:  if `module` is False, or
        is None but cannot be found automatically, then all objects are
        considered to belong to the (non-existent) module, so all contained
        objects will (recursively) be searched for doctests.

        The globals for each DocTest is formed by combining `globs`
        and `extraglobs` (bindings in `extraglobs` override bindings
        in `globs`).  A new copy of the globals dictionary is created
        for each DocTest.  If `globs` is not specified, then it
        defaults to the module's `__dict__`, if specified, or {}
        otherwise.  If `extraglobs` is not specified, then it defaults
        to {}.

        """
        # If name was not specified, then extract it from the object.
        if name is None:
            name = getattr(obj, '__name__', None)
            if name is None:
                raise ValueError("DocTestFinder.find: name must be given "
                        "when obj.__name__ doesn't exist: %r" %
                                 (type(obj),))

        # Find the module that contains the given object (if obj is
        # a module, then module=obj.).  Note: this may fail, in which
        # case module will be None.
        if module is False:
            module = None
        elif module is None:
            module = inspect.getmodule(obj)

        # Read the module's source code.  This is used by
        # DocTestFinder._find_lineno to find the line number for a
        # given object's docstring.
        try:
            file = inspect.getsourcefile(obj) or inspect.getfile(obj)
            source_lines = linecache.getlines(file)
            if not source_lines:
                source_lines = None
        except TypeError:
            source_lines = None

        # Initialize globals, and merge in extraglobs.
        if globs is None:
            if module is None:
                globs = {}
            else:
                globs = module.__dict__.copy()
        else:
            globs = globs.copy()
        if extraglobs is not None:
            globs.update(extraglobs)

        # Recursively expore `obj`, extracting DocTests.
        tests = []
        self._find(tests, obj, name, module, source_lines, globs, {})
        return tests

    def _filter(self, obj, prefix, base):
        """
        Return true if the given object should not be examined.
        """
        return (self._namefilter is not None and
                self._namefilter(prefix, base))

    def _from_module(self, module, object):
        """
        Return true if the given object is defined in the given
        module.
        """
        if module is None:
            return True
        elif inspect.isfunction(object):
            return module.__dict__ is object.func_globals
        elif inspect.isclass(object):
            return module.__name__ == object.__module__
        elif inspect.getmodule(object) is not None:
            return module is inspect.getmodule(object)
        elif hasattr(object, '__module__'):
            return module.__name__ == object.__module__
        elif isinstance(object, property):
            return True # [XX] no way not be sure.
        else:
            raise ValueError("object must be a class or function")

    def _find(self, tests, obj, name, module, source_lines, globs, seen):
        """
        Find tests for the given object and any contained objects, and
        add them to `tests`.
        """
        if self._verbose:
            print 'Finding tests in %s' % name

        # If we've already processed this object, then ignore it.
        if id(obj) in seen:
            return
        seen[id(obj)] = 1

        # Find a test for this object, and add it to the list of tests.
        test = self._get_test(obj, name, module, globs, source_lines)
        if test is not None:
            tests.append(test)

        # Look for tests in a module's contained objects.
        if inspect.ismodule(obj) and self._recurse:
            for valname, val in obj.__dict__.items():
                # Check if this contained object should be ignored.
                if self._filter(val, name, valname):
                    continue
                valname = '%s.%s' % (name, valname)
                # Recurse to functions & classes.
                if ((inspect.isfunction(val) or inspect.isclass(val)) and
                    self._from_module(module, val)):
                    self._find(tests, val, valname, module, source_lines,
                               globs, seen)

        # Look for tests in a module's __test__ dictionary.
        if inspect.ismodule(obj) and self._recurse:
            for valname, val in getattr(obj, '__test__', {}).items():
                if not isinstance(valname, basestring):
                    raise ValueError("DocTestFinder.find: __test__ keys "
                                     "must be strings: %r" %
                                     (type(valname),))
                if not (inspect.isfunction(val) or inspect.isclass(val) or
                        inspect.ismethod(val) or inspect.ismodule(val) or
                        isinstance(val, basestring)):
                    raise ValueError("DocTestFinder.find: __test__ values "
                                     "must be strings, functions, methods, "
                                     "classes, or modules: %r" %
                                     (type(val),))
                valname = '%s.__test__.%s' % (name, valname)
                self._find(tests, val, valname, module, source_lines,
                           globs, seen)

        # Look for tests in a class's contained objects.
        if inspect.isclass(obj) and self._recurse:
            for valname, val in obj.__dict__.items():
                # Check if this contained object should be ignored.
                if self._filter(val, name, valname):
                    continue
                # Special handling for staticmethod/classmethod.
                if isinstance(val, staticmethod):
                    val = getattr(obj, valname)
                if isinstance(val, classmethod):
                    val = getattr(obj, valname).im_func

                # Recurse to methods, properties, and nested classes.
                if ((inspect.isfunction(val) or inspect.isclass(val) or
                      isinstance(val, property)) and
                      self._from_module(module, val)):
                    valname = '%s.%s' % (name, valname)
                    self._find(tests, val, valname, module, source_lines,
                               globs, seen)

    def _get_test(self, obj, name, module, globs, source_lines):
        """
        Return a DocTest for the given object, if it defines a docstring;
        otherwise, return None.
        """
        # Extract the object's docstring.  If it doesn't have one,
        # then return None (no test for this object).
        if isinstance(obj, basestring):
            docstring = obj
        else:
            try:
                if obj.__doc__ is None:
                    docstring = ''
                else:
                    docstring = obj.__doc__
                    if not isinstance(docstring, basestring):
                        docstring = str(docstring)
            except (TypeError, AttributeError):
                docstring = ''

        # Find the docstring's location in the file.
        lineno = self._find_lineno(obj, source_lines)

        # Don't bother if the docstring is empty.
        if self._exclude_empty and not docstring:
            return None

        # Return a DocTest for this object.
        if module is None:
            filename = None
        else:
            filename = getattr(module, '__file__', module.__name__)
            if filename[-4:] in (".pyc", ".pyo"):
                filename = filename[:-1]
        return self._parser.get_doctest(docstring, globs, name,
                                        filename, lineno)

    def _find_lineno(self, obj, source_lines):
        """
        Return a line number of the given object's docstring.  Note:
        this method assumes that the object has a docstring.
        """
        lineno = None

        # Find the line number for modules.
        if inspect.ismodule(obj):
            lineno = 0

        # Find the line number for classes.
        # Note: this could be fooled if a class is defined multiple
        # times in a single file.
        if inspect.isclass(obj):
            if source_lines is None:
                return None
            pat = re.compile(r'^\s*class\s*%s\b' %
                             getattr(obj, '__name__', '-'))
            for i, line in enumerate(source_lines):
                if pat.match(line):
                    lineno = i
                    break

        # Find the line number for functions & methods.
        if inspect.ismethod(obj): obj = obj.im_func
        if inspect.isfunction(obj): obj = obj.func_code
        if inspect.istraceback(obj): obj = obj.tb_frame
        if inspect.isframe(obj): obj = obj.f_code
        if inspect.iscode(obj):
            lineno = getattr(obj, 'co_firstlineno', None)-1

        # Find the line number where the docstring starts.  Assume
        # that it's the first line that begins with a quote mark.
        # Note: this could be fooled by a multiline function
        # signature, where a continuation line begins with a quote
        # mark.
        if lineno is not None:
            if source_lines is None:
                return lineno+1
            pat = re.compile('(^|.*:)\s*\w*("|\')')
            for lineno in range(lineno, len(source_lines)):
                if pat.match(source_lines[lineno]):
                    return lineno

        # We couldn't find the line number.
        return None

######################################################################
## 5. DocTest Runner
######################################################################

class DocTestRunner:
    """
    A class used to run DocTest test cases, and accumulate statistics.
    The `run` method is used to process a single DocTest case.  It
    returns a tuple `(f, t)`, where `t` is the number of test cases
    tried, and `f` is the number of test cases that failed.

        >>> tests = DocTestFinder().find(_TestClass)
        >>> runner = DocTestRunner(verbose=False)
        >>> for test in tests:
        ...     print runner.run(test)
        (0, 2)
        (0, 1)
        (0, 2)
        (0, 2)

    The `summarize` method prints a summary of all the test cases that
    have been run by the runner, and returns an aggregated `(f, t)`
    tuple:

        >>> runner.summarize(verbose=1)
        4 items passed all tests:
           2 tests in _TestClass
           2 tests in _TestClass.__init__
           2 tests in _TestClass.get
           1 tests in _TestClass.square
        7 tests in 4 items.
        7 passed and 0 failed.
        Test passed.
        (0, 7)

    The aggregated number of tried examples and failed examples is
    also available via the `tries` and `failures` attributes:

        >>> runner.tries
        7
        >>> runner.failures
        0

    The comparison between expected outputs and actual outputs is done
    by an `OutputChecker`.  This comparison may be customized with a
    number of option flags; see the documentation for `testmod` for
    more information.  If the option flags are insufficient, then the
    comparison may also be customized by passing a subclass of
    `OutputChecker` to the constructor.

    The test runner's display output can be controlled in two ways.
    First, an output function (`out) can be passed to
    `TestRunner.run`; this function will be called with strings that
    should be displayed.  It defaults to `sys.stdout.write`.  If
    capturing the output is not sufficient, then the display output
    can be also customized by subclassing DocTestRunner, and
    overriding the methods `report_start`, `report_success`,
    `report_unexpected_exception`, and `report_failure`.
    """
    # This divider string is used to separate failure messages, and to
    # separate sections of the summary.
    DIVIDER = "*" * 70

    def __init__(self, checker=None, verbose=None, optionflags=0):
        """
        Create a new test runner.

        Optional keyword arg `checker` is the `OutputChecker` that
        should be used to compare the expected outputs and actual
        outputs of doctest examples.

        Optional keyword arg 'verbose' prints lots of stuff if true,
        only failures if false; by default, it's true iff '-v' is in
        sys.argv.

        Optional argument `optionflags` can be used to control how the
        test runner compares expected output to actual output, and how
        it displays failures.  See the documentation for `testmod` for
        more information.
        """
        self._checker = checker or OutputChecker()
        if verbose is None:
            verbose = '-v' in sys.argv
        self._verbose = verbose
        self.optionflags = optionflags
        self.original_optionflags = optionflags

        # Keep track of the examples we've run.
        self.tries = 0
        self.failures = 0
        self._name2ft = {}

        # Create a fake output target for capturing doctest output.
        self._fakeout = _SpoofOut()

    #/////////////////////////////////////////////////////////////////
    # Reporting methods
    #/////////////////////////////////////////////////////////////////

    def report_start(self, out, test, example):
        """
        Report that the test runner is about to process the given
        example.  (Only displays a message if verbose=True)
        """
        if self._verbose:
            if example.want:
                out('Trying:\n' + _indent(example.source) +
                    'Expecting:\n' + _indent(example.want))
            else:
                out('Trying:\n' + _indent(example.source) +
                    'Expecting nothing\n')

    def report_success(self, out, test, example, got):
        """
        Report that the given example ran successfully.  (Only
        displays a message if verbose=True)
        """
        if self._verbose:
            out("ok\n")

    def report_failure(self, out, test, example, got):
        """
        Report that the given example failed.
        """
        out(self._failure_header(test, example) +
            self._checker.output_difference(example, got, self.optionflags))

    def report_unexpected_exception(self, out, test, example, exc_info):
        """
        Report that the given example raised an unexpected exception.
        """
        out(self._failure_header(test, example) +
            'Exception raised:\n' + _indent(_exception_traceback(exc_info)))

    def _failure_header(self, test, example):
        out = [self.DIVIDER]
        if test.filename:
            if test.lineno is not None and example.lineno is not None:
                lineno = test.lineno + example.lineno + 1
            else:
                lineno = '?'
            out.append('File "%s", line %s, in %s' %
                       (test.filename, lineno, test.name))
        else:
            out.append('Line %s, in %s' % (example.lineno+1, test.name))
        out.append('Failed example:')
        source = example.source
        out.append(_indent(source))
        return '\n'.join(out)

    #/////////////////////////////////////////////////////////////////
    # DocTest Running
    #/////////////////////////////////////////////////////////////////

    def __run(self, test, compileflags, out):
        """
        Run the examples in `test`.  Write the outcome of each example
        with one of the `DocTestRunner.report_*` methods, using the
        writer function `out`.  `compileflags` is the set of compiler
        flags that should be used to execute examples.  Return a tuple
        `(f, t)`, where `t` is the number of examples tried, and `f`
        is the number of examples that failed.  The examples are run
        in the namespace `test.globs`.
        """
        # Keep track of the number of failures and tries.
        failures = tries = 0

        # Save the option flags (since option directives can be used
        # to modify them).
        original_optionflags = self.optionflags

        SUCCESS, FAILURE, BOOM = range(3) # `outcome` state

        check = self._checker.check_output

        # Process each example.
        for examplenum, example in enumerate(test.examples):

            # If REPORT_ONLY_FIRST_FAILURE is set, then supress
            # reporting after the first failure.
            quiet = (self.optionflags & REPORT_ONLY_FIRST_FAILURE and
                     failures > 0)

            # Merge in the example's options.
            self.optionflags = original_optionflags
            if example.options:
                for (optionflag, val) in example.options.items():
                    if val:
                        self.optionflags |= optionflag
                    else:
                        self.optionflags &= ~optionflag

            # Record that we started this example.
            tries += 1
            if not quiet:
                self.report_start(out, test, example)

            # Use a special filename for compile(), so we can retrieve
            # the source code during interactive debugging (see
            # __patched_linecache_getlines).
            filename = '<doctest %s[%d]>' % (test.name, examplenum)

            # Run the example in the given context (globs), and record
            # any exception that gets raised.  (But don't intercept
            # keyboard interrupts.)
            try:
                # Don't blink!  This is where the user's code gets run.
                exec compile(example.source, filename, "single",
                             compileflags, 1) in test.globs
                self.debugger.set_continue() # ==== Example Finished ====
                exception = None
            except KeyboardInterrupt:
                raise
            except:
                exception = sys.exc_info()
                self.debugger.set_continue() # ==== Example Finished ====

            got = self._fakeout.getvalue()  # the actual output
            self._fakeout.truncate(0)
            outcome = FAILURE   # guilty until proved innocent or insane

            # If the example executed without raising any exceptions,
            # verify its output.
            if exception is None:
                if check(example.want, got, self.optionflags):
                    outcome = SUCCESS

            # The example raised an exception:  check if it was expected.
            else:
                exc_info = sys.exc_info()
                exc_msg = traceback.f…