run-tests: add docstrings

tests/run-tests.py

@@ -1,1768 +1,1785 b''
 #!/usr/bin/env python
 #
 # run-tests.py - Run a set of tests on Mercurial
 #
 # Copyright 2006 Matt Mackall <[e-mail]>
 #
 # This software may be used and distributed according to the terms of the
 # GNU General Public License version 2 or any later version.
 
 # Modifying this script is tricky because it has many modes:
 #   - serial (default) vs parallel (-jN, N > 1)
 #   - no coverage (default) vs coverage (-c, -C, -s)
 #   - temp install (default) vs specific hg script (--with-hg, --local)
 #   - tests are a mix of shell scripts and Python scripts
 #
 # If you change this script, it is recommended that you ensure you
 # haven't broken it by running it in various modes with a representative
 # sample of test scripts.  For example:
 #
 #  1) serial, no coverage, temp install:
 #      ./run-tests.py test-s*
 #  2) serial, no coverage, local hg:
 #      ./run-tests.py --local test-s*
 #  3) serial, coverage, temp install:
 #      ./run-tests.py -c test-s*
 #  4) serial, coverage, local hg:
 #      ./run-tests.py -c --local test-s*      # unsupported
 #  5) parallel, no coverage, temp install:
 #      ./run-tests.py -j2 test-s*
 #  6) parallel, no coverage, local hg:
 #      ./run-tests.py -j2 --local test-s*
 #  7) parallel, coverage, temp install:
 #      ./run-tests.py -j2 -c test-s*          # currently broken
 #  8) parallel, coverage, local install:
 #      ./run-tests.py -j2 -c --local test-s*  # unsupported (and broken)
 #  9) parallel, custom tmp dir:
 #      ./run-tests.py -j2 --tmpdir /tmp/myhgtests
 #
 # (You could use any subset of the tests: test-s* happens to match
 # enough that it's worth doing parallel runs, few enough that it
 # completes fairly quickly, includes both shell and Python scripts, and
 # includes some scripts that run daemon processes.)
 
 from distutils import version
 import difflib
 import errno
 import optparse
 import os
 import shutil
 import subprocess
 import signal
 import sys
 import tempfile
 import time
 import random
 import re
 import threading
 import killdaemons as killmod
 import Queue as queue
 import unittest
 
 processlock = threading.Lock()
 
 # subprocess._cleanup can race with any Popen.wait or Popen.poll on py24
 # http://bugs.python.org/issue1731717 for details. We shouldn't be producing
 # zombies but it's pretty harmless even if we do.
 if sys.version_info < (2, 5):
     subprocess._cleanup = lambda: None
 
 closefds = os.name == 'posix'
 def Popen4(cmd, wd, timeout, env=None):
     processlock.acquire()
     p = subprocess.Popen(cmd, shell=True, bufsize=-1, cwd=wd, env=env,
                          close_fds=closefds,
                          stdin=subprocess.PIPE, stdout=subprocess.PIPE,
                          stderr=subprocess.STDOUT)
     processlock.release()
 
     p.fromchild = p.stdout
     p.tochild = p.stdin
     p.childerr = p.stderr
 
     p.timeout = False
     if timeout:
         def t():
             start = time.time()
             while time.time() - start < timeout and p.returncode is None:
                 time.sleep(.1)
             p.timeout = True
             if p.returncode is None:
                 terminate(p)
         threading.Thread(target=t).start()
 
     return p
 
 PYTHON = sys.executable.replace('\\', '/')
 IMPL_PATH = 'PYTHONPATH'
 if 'java' in sys.platform:
     IMPL_PATH = 'JYTHONPATH'
 
 TESTDIR = HGTMP = INST = BINDIR = TMPBINDIR = PYTHONDIR = None
 
 defaults = {
     'jobs': ('HGTEST_JOBS', 1),
     'timeout': ('HGTEST_TIMEOUT', 180),
     'port': ('HGTEST_PORT', 20059),
     'shell': ('HGTEST_SHELL', 'sh'),
 }
 
 def parselistfiles(files, listtype, warn=True):
     entries = dict()
     for filename in files:
         try:
             path = os.path.expanduser(os.path.expandvars(filename))
             f = open(path, "r")
         except IOError, err:
             if err.errno != errno.ENOENT:
                 raise
             if warn:
                 print "warning: no such %s file: %s" % (listtype, filename)
             continue
 
         for line in f.readlines():
             line = line.split('#', 1)[0].strip()
             if line:
                 entries[line] = filename
 
         f.close()
     return entries
 
 def getparser():
     """Obtain the OptionParser used by the CLI."""
     parser = optparse.OptionParser("%prog [options] [tests]")
 
     # keep these sorted
     parser.add_option("--blacklist", action="append",
         help="skip tests listed in the specified blacklist file")
     parser.add_option("--whitelist", action="append",
         help="always run tests listed in the specified whitelist file")
     parser.add_option("--changed", type="string",
         help="run tests that are changed in parent rev or working directory")
     parser.add_option("-C", "--annotate", action="store_true",
         help="output files annotated with coverage")
     parser.add_option("-c", "--cover", action="store_true",
         help="print a test coverage report")
     parser.add_option("-d", "--debug", action="store_true",
         help="debug mode: write output of test scripts to console"
              " rather than capturing and diffing it (disables timeout)")
     parser.add_option("-f", "--first", action="store_true",
         help="exit on the first test failure")
     parser.add_option("-H", "--htmlcov", action="store_true",
         help="create an HTML report of the coverage of the files")
     parser.add_option("-i", "--interactive", action="store_true",
         help="prompt to accept changed output")
     parser.add_option("-j", "--jobs", type="int",
         help="number of jobs to run in parallel"
              " (default: $%s or %d)" % defaults['jobs'])
     parser.add_option("--keep-tmpdir", action="store_true",
         help="keep temporary directory after running tests")
     parser.add_option("-k", "--keywords",
         help="run tests matching keywords")
     parser.add_option("-l", "--local", action="store_true",
         help="shortcut for --with-hg=<testdir>/../hg")
     parser.add_option("--loop", action="store_true",
         help="loop tests repeatedly")
     parser.add_option("-n", "--nodiff", action="store_true",
         help="skip showing test changes")
     parser.add_option("-p", "--port", type="int",
         help="port on which servers should listen"
              " (default: $%s or %d)" % defaults['port'])
     parser.add_option("--compiler", type="string",
         help="compiler to build with")
     parser.add_option("--pure", action="store_true",
         help="use pure Python code instead of C extensions")
     parser.add_option("-R", "--restart", action="store_true",
         help="restart at last error")
     parser.add_option("-r", "--retest", action="store_true",
         help="retest failed tests")
     parser.add_option("-S", "--noskips", action="store_true",
         help="don't report skip tests verbosely")
     parser.add_option("--shell", type="string",
         help="shell to use (default: $%s or %s)" % defaults['shell'])
     parser.add_option("-t", "--timeout", type="int",
         help="kill errant tests after TIMEOUT seconds"
              " (default: $%s or %d)" % defaults['timeout'])
     parser.add_option("--time", action="store_true",
         help="time how long each test takes")
     parser.add_option("--tmpdir", type="string",
         help="run tests in the given temporary directory"
              " (implies --keep-tmpdir)")
     parser.add_option("-v", "--verbose", action="store_true",
         help="output verbose messages")
     parser.add_option("--view", type="string",
         help="external diff viewer")
     parser.add_option("--with-hg", type="string",
         metavar="HG",
         help="test using specified hg script rather than a "
              "temporary installation")
     parser.add_option("-3", "--py3k-warnings", action="store_true",
         help="enable Py3k warnings on Python 2.6+")
     parser.add_option('--extra-config-opt', action="append",
                       help='set the given config opt in the test hgrc')
     parser.add_option('--random', action="store_true",
                       help='run tests in random order')
 
     for option, (envvar, default) in defaults.items():
         defaults[option] = type(default)(os.environ.get(envvar, default))
     parser.set_defaults(**defaults)
 
     return parser
 
 def parseargs(args, parser):
     """Parse arguments with our OptionParser and validate results."""
     (options, args) = parser.parse_args(args)
 
     # jython is always pure
     if 'java' in sys.platform or '__pypy__' in sys.modules:
         options.pure = True
 
     if options.with_hg:
         options.with_hg = os.path.expanduser(options.with_hg)
         if not (os.path.isfile(options.with_hg) and
                 os.access(options.with_hg, os.X_OK)):
             parser.error('--with-hg must specify an executable hg script')
         if not os.path.basename(options.with_hg) == 'hg':
             sys.stderr.write('warning: --with-hg should specify an hg script\n')
     if options.local:
         testdir = os.path.dirname(os.path.realpath(sys.argv[0]))
         hgbin = os.path.join(os.path.dirname(testdir), 'hg')
         if os.name != 'nt' and not os.access(hgbin, os.X_OK):
             parser.error('--local specified, but %r not found or not executable'
                          % hgbin)
         options.with_hg = hgbin
 
     options.anycoverage = options.cover or options.annotate or options.htmlcov
     if options.anycoverage:
         try:
             import coverage
             covver = version.StrictVersion(coverage.__version__).version
             if covver < (3, 3):
                 parser.error('coverage options require coverage 3.3 or later')
         except ImportError:
             parser.error('coverage options now require the coverage package')
 
     if options.anycoverage and options.local:
         # this needs some path mangling somewhere, I guess
         parser.error("sorry, coverage options do not work when --local "
                      "is specified")
 
     global verbose
     if options.verbose:
         verbose = ''
 
     if options.tmpdir:
         options.tmpdir = os.path.expanduser(options.tmpdir)
 
     if options.jobs < 1:
         parser.error('--jobs must be positive')
     if options.interactive and options.debug:
         parser.error("-i/--interactive and -d/--debug are incompatible")
     if options.debug:
         if options.timeout != defaults['timeout']:
             sys.stderr.write(
                 'warning: --timeout option ignored with --debug\n')
         options.timeout = 0
     if options.py3k_warnings:
         if sys.version_info[:2] < (2, 6) or sys.version_info[:2] >= (3, 0):
             parser.error('--py3k-warnings can only be used on Python 2.6+')
     if options.blacklist:
         options.blacklist = parselistfiles(options.blacklist, 'blacklist')
     if options.whitelist:
         options.whitelisted = parselistfiles(options.whitelist, 'whitelist')
     else:
         options.whitelisted = {}
 
     return (options, args)
 
 def rename(src, dst):
     """Like os.rename(), trade atomicity and opened files friendliness
     for existing destination support.
     """
     shutil.copy(src, dst)
     os.remove(src)
 
 def getdiff(expected, output, ref, err):
     servefail = False
     lines = []
     for line in difflib.unified_diff(expected, output, ref, err):
         lines.append(line)
         if not servefail and line.startswith(
                              '+  abort: child process failed to start'):
             servefail = True
 
     return servefail, lines
 
 verbose = False
 def vlog(*msg):
     """Log only when in verbose mode."""
     if verbose is False:
         return
 
     return log(*msg)
 
 def log(*msg):
     """Log something to stdout.
 
     Arguments are strings to print.
     """
     iolock.acquire()
     if verbose:
         print verbose,
     for m in msg:
         print m,
     print
     sys.stdout.flush()
     iolock.release()
 
 def terminate(proc):
     """Terminate subprocess (with fallback for Python versions < 2.6)"""
     vlog('# Terminating process %d' % proc.pid)
     try:
         getattr(proc, 'terminate', lambda : os.kill(proc.pid, signal.SIGTERM))()
     except OSError:
         pass
 
 def killdaemons(pidfile):
     return killmod.killdaemons(pidfile, tryhard=False, remove=True,
                                logfn=vlog)
 
 class Test(unittest.TestCase):
     """Encapsulates a single, runnable test.
 
     While this class conforms to the unittest.TestCase API, it differs in that
     instances need to be instantiated manually. (Typically, unittest.TestCase
     classes are instantiated automatically by scanning modules.)
     """
 
     # Status code reserved for skipped tests (used by hghave).
     SKIPPED_STATUS = 80
 
     def __init__(self, path, tmpdir, keeptmpdir=False,
                  debug=False,
                  timeout=defaults['timeout'],
                  startport=defaults['port'], extraconfigopts=None,
                  py3kwarnings=False, shell=None):
         """Create a test from parameters.
 
         path is the full path to the file defining the test.
 
         tmpdir is the main temporary directory to use for this test.
 
         keeptmpdir determines whether to keep the test's temporary directory
         after execution. It defaults to removal (False).
 
         debug mode will make the test execute verbosely, with unfiltered
         output.
 
         timeout controls the maximum run time of the test. It is ignored when
         debug is True.
 
         startport controls the starting port number to use for this test. Each
         test will reserve 3 port numbers for execution. It is the caller's
         responsibility to allocate a non-overlapping port range to Test
         instances.
 
         extraconfigopts is an iterable of extra hgrc config options. Values
         must have the form "key=value" (something understood by hgrc). Values
         of the form "foo.key=value" will result in "[foo] key=value".
 
         py3kwarnings enables Py3k warnings.
 
         shell is the shell to execute tests in.
         """
 
         self.path = path
         self.name = os.path.basename(path)
         self._testdir = os.path.dirname(path)
         self.errpath = os.path.join(self._testdir, '%s.err' % self.name)
 
         self._threadtmp = tmpdir
         self._keeptmpdir = keeptmpdir
         self._debug = debug
         self._timeout = timeout
         self._startport = startport
         self._extraconfigopts = extraconfigopts or []
         self._py3kwarnings = py3kwarnings
         self._shell = shell
 
         self._aborted = False
         self._daemonpids = []
         self._finished = None
         self._ret = None
         self._out = None
         self._skipped = None
         self._testtmp = None
 
         # If we're not in --debug mode and reference output file exists,
         # check test output against it.
         if debug:
             self._refout = None # to match "out is None"
         elif os.path.exists(self.refpath):
             f = open(self.refpath, 'r')
             self._refout = f.read().splitlines(True)
             f.close()
         else:
             self._refout = []
 
     def __str__(self):
         return self.name
 
     def shortDescription(self):
         return self.name
 
     def setUp(self):
         """Tasks to perform before run()."""
         self._finished = False
         self._ret = None
         self._out = None
         self._skipped = None
 
         try:
             os.mkdir(self._threadtmp)
         except OSError, e:
             if e.errno != errno.EEXIST:
                 raise
 
         self._testtmp = os.path.join(self._threadtmp,
                                      os.path.basename(self.path))
         os.mkdir(self._testtmp)
 
         # Remove any previous output files.
         if os.path.exists(self.errpath):
             os.remove(self.errpath)
 
     def run(self, result):
+        """Run this test and report results against a TestResult instance."""
+        # This function is extremely similar to unittest.TestCase.run(). Once
+        # we require Python 2.7 (or at least its version of unittest), this
+        # function can largely go away.
         self._result = result
         result.startTest(self)
         try:
             try:
                 self.setUp()
             except (KeyboardInterrupt, SystemExit):
                 self._aborted = True
                 raise
             except Exception:
                 result.addError(self, sys.exc_info())
                 return
 
             success = False
             try:
                 self.runTest()
             except KeyboardInterrupt:
                 self._aborted = True
                 raise
             except SkipTest, e:
                 result.addSkip(self, str(e))
             except IgnoreTest, e:
                 result.addIgnore(self, str(e))
             except WarnTest, e:
                 result.addWarn(self, str(e))
             except self.failureException, e:
                 # This differs from unittest in that we don't capture
                 # the stack trace. This is for historical reasons and
                 # this decision could be revisted in the future,
                 # especially for PythonTest instances.
                 result.addFailure(self, str(e))
             except Exception:
                 result.addError(self, sys.exc_info())
             else:
                 success = True
 
             try:
                 self.tearDown()
             except (KeyboardInterrupt, SystemExit):
                 self._aborted = True
                 raise
             except Exception:
                 result.addError(self, sys.exc_info())
                 success = False
 
             if success:
                 result.addSuccess(self)
         finally:
             result.stopTest(self, interrupted=self._aborted)
 
     def runTest(self):
         """Run this test instance.
 
         This will return a tuple describing the result of the test.
         """
         replacements = self._getreplacements()
         env = self._getenv()
         self._daemonpids.append(env['DAEMON_PIDS'])
         self._createhgrc(env['HGRCPATH'])
 
         vlog('# Test', self.name)
 
         ret, out = self._run(replacements, env)
         self._finished = True
         self._ret = ret
         self._out = out
 
         def describe(ret):
             if ret < 0:
                 return 'killed by signal: %d' % -ret
             return 'returned error code %d' % ret
 
         self._skipped = False
 
         if ret == self.SKIPPED_STATUS:
             if out is None: # Debug mode, nothing to parse.
                 missing = ['unknown']
                 failed = None
             else:
                 missing, failed = TTest.parsehghaveoutput(out)
 
             if not missing:
                 missing = ['irrelevant']
 
             if failed:
                 self.fail('hg have failed checking for %s' % failed[-1])
             else:
                 self._skipped = True
                 raise SkipTest(missing[-1])
         elif ret == 'timeout':
             self.fail('timed out')
         elif ret is False:
             raise WarnTest('no result code from test')
         elif out != self._refout:
             # The result object handles diff calculation for us.
             self._result.addOutputMismatch(self, ret, out, self._refout)
 
             if ret:
                 msg = 'output changed and ' + describe(ret)
             else:
                 msg = 'output changed'
 
             if (ret != 0 or out != self._refout) and not self._skipped \
                 and not self._debug:
                 f = open(self.errpath, 'wb')
                 for line in out:
                     f.write(line)
             f.close()
 
             self.fail(msg)
         elif ret:
             self.fail(describe(ret))
 
     def tearDown(self):
         """Tasks to perform after run()."""
         for entry in self._daemonpids:
             killdaemons(entry)
         self._daemonpids = []
 
         if not self._keeptmpdir:
             shutil.rmtree(self._testtmp, True)
             shutil.rmtree(self._threadtmp, True)
 
         if (self._ret != 0 or self._out != self._refout) and not self._skipped \
             and not self._debug and self._out:
             f = open(self.errpath, 'wb')
             for line in self._out:
                 f.write(line)
             f.close()
 
         vlog("# Ret was:", self._ret)
 
     def _run(self, replacements, env):
         # This should be implemented in child classes to run tests.
         raise SkipTest('unknown test type')
 
     def abort(self):
         """Terminate execution of this test."""
         self._aborted = True
 
     def _getreplacements(self):
+        """Obtain a mapping of text replacements to apply to test output.
+
+        Test output needs to be normalized so it can be compared to expected
+        output. This function defines how some of that normalization will
+        occur.
+        """
         r = [
             (r':%s\b' % self._startport, ':$HGPORT'),
             (r':%s\b' % (self._startport + 1), ':$HGPORT1'),
             (r':%s\b' % (self._startport + 2), ':$HGPORT2'),
             ]
 
         if os.name == 'nt':
             r.append(
                 (''.join(c.isalpha() and '[%s%s]' % (c.lower(), c.upper()) or
                     c in '/\\' and r'[/\\]' or c.isdigit() and c or '\\' + c
                     for c in self._testtmp), '$TESTTMP'))
         else:
             r.append((re.escape(self._testtmp), '$TESTTMP'))
 
         return r
 
     def _getenv(self):
+        """Obtain environment variables to use during test execution."""
         env = os.environ.copy()
         env['TESTTMP'] = self._testtmp
         env['HOME'] = self._testtmp
         env["HGPORT"] = str(self._startport)
         env["HGPORT1"] = str(self._startport + 1)
         env["HGPORT2"] = str(self._startport + 2)
         env["HGRCPATH"] = os.path.join(self._threadtmp, '.hgrc')
         env["DAEMON_PIDS"] = os.path.join(self._threadtmp, 'daemon.pids')
         env["HGEDITOR"] = sys.executable + ' -c "import sys; sys.exit(0)"'
         env["HGMERGE"] = "internal:merge"
         env["HGUSER"]   = "test"
         env["HGENCODING"] = "ascii"
         env["HGENCODINGMODE"] = "strict"
 
         # Reset some environment variables to well-known values so that
         # the tests produce repeatable output.
         env['LANG'] = env['LC_ALL'] = env['LANGUAGE'] = 'C'
         env['TZ'] = 'GMT'
         env["EMAIL"] = "Foo Bar <[e-mail]>"
         env['COLUMNS'] = '80'
         env['TERM'] = 'xterm'
 
         for k in ('HG HGPROF CDPATH GREP_OPTIONS http_proxy no_proxy ' +
                   'NO_PROXY').split():
             if k in env:
                 del env[k]
 
         # unset env related to hooks
         for k in env.keys():
             if k.startswith('HG_'):
                 del env[k]
 
         return env
 
     def _createhgrc(self, path):
-        # create a fresh hgrc
+        """Create an hgrc file for this test."""
         hgrc = open(path, 'w')
         hgrc.write('[ui]\n')
         hgrc.write('slash = True\n')
         hgrc.write('interactive = False\n')
         hgrc.write('[defaults]\n')
         hgrc.write('backout = -d "0 0"\n')
         hgrc.write('commit = -d "0 0"\n')
         hgrc.write('shelve = --date "0 0"\n')
         hgrc.write('tag = -d "0 0"\n')
         for opt in self._extraconfigopts:
             section, key = opt.split('.', 1)
             assert '=' in key, ('extra config opt %s must '
                                 'have an = for assignment' % opt)
             hgrc.write('[%s]\n%s\n' % (section, key))
         hgrc.close()
 
     def fail(self, msg):
         # unittest differentiates between errored and failed.
         # Failed is denoted by AssertionError (by default at least).
         raise AssertionError(msg)
 
 class PythonTest(Test):
     """A Python-based test."""
 
     @property
     def refpath(self):
         return os.path.join(self._testdir, '%s.out' % self.name)
 
     def _run(self, replacements, env):
         py3kswitch = self._py3kwarnings and ' -3' or ''
         cmd = '%s%s "%s"' % (PYTHON, py3kswitch, self.path)
         vlog("# Running", cmd)
         if os.name == 'nt':
             replacements.append((r'\r\n', '\n'))
         result = run(cmd, self._testtmp, replacements, env,
                    debug=self._debug, timeout=self._timeout)
         if self._aborted:
             raise KeyboardInterrupt()
 
         return result
 
 class TTest(Test):
     """A "t test" is a test backed by a .t file."""
 
     SKIPPED_PREFIX = 'skipped: '
     FAILED_PREFIX = 'hghave check failed: '
     NEEDESCAPE = re.compile(r'[\x00-\x08\x0b-\x1f\x7f-\xff]').search
 
     ESCAPESUB = re.compile(r'[\x00-\x08\x0b-\x1f\\\x7f-\xff]').sub
     ESCAPEMAP = dict((chr(i), r'\x%02x' % i) for i in range(256)).update(
                      {'\\': '\\\\', '\r': r'\r'})
 
     @property
     def refpath(self):
         return os.path.join(self._testdir, self.name)
 
     def _run(self, replacements, env):
         f = open(self.path)
         lines = f.readlines()
         f.close()
 
         salt, script, after, expected = self._parsetest(lines)
 
         # Write out the generated script.
         fname = '%s.sh' % self._testtmp
         f = open(fname, 'w')
         for l in script:
             f.write(l)
         f.close()
 
         cmd = '%s "%s"' % (self._shell, fname)
         vlog("# Running", cmd)
 
         exitcode, output = run(cmd, self._testtmp, replacements, env,
                                debug=self._debug, timeout=self._timeout)
 
         if self._aborted:
             raise KeyboardInterrupt()
 
         # Do not merge output if skipped. Return hghave message instead.
         # Similarly, with --debug, output is None.
         if exitcode == self.SKIPPED_STATUS or output is None:
             return exitcode, output
 
         return self._processoutput(exitcode, output, salt, after, expected)
 
     def _hghave(self, reqs):
         # TODO do something smarter when all other uses of hghave are gone.
         tdir = self._testdir.replace('\\', '/')
         proc = Popen4('%s -c "%s/hghave %s"' %
                       (self._shell, tdir, ' '.join(reqs)),
                       self._testtmp, 0)
         stdout, stderr = proc.communicate()
         ret = proc.wait()
         if wifexited(ret):
             ret = os.WEXITSTATUS(ret)
         if ret == 2:
             print stdout
             sys.exit(1)
 
         return ret == 0
 
     def _parsetest(self, lines):
         # We generate a shell script which outputs unique markers to line
         # up script results with our source. These markers include input
         # line number and the last return code.
         salt = "SALT" + str(time.time())
         def addsalt(line, inpython):
             if inpython:
                 script.append('%s %d 0\n' % (salt, line))
             else:
                 script.append('echo %s %s $?\n' % (salt, line))
 
         script = []
 
         # After we run the shell script, we re-unify the script output
         # with non-active parts of the source, with synchronization by our
         # SALT line number markers. The after table contains the non-active
         # components, ordered by line number.
         after = {}
 
         # Expected shell script output.
         expected = {}
 
         pos = prepos = -1
 
         # True or False when in a true or false conditional section
         skipping = None
 
         # We keep track of whether or not we're in a Python block so we
         # can generate the surrounding doctest magic.
         inpython = False
 
         if self._debug:
             script.append('set -x\n')
         if os.getenv('MSYSTEM'):
             script.append('alias pwd="pwd -W"\n')
 
         for n, l in enumerate(lines):
             if not l.endswith('\n'):
                 l += '\n'
             if l.startswith('#if'):
                 lsplit = l.split()
                 if len(lsplit) < 2 or lsplit[0] != '#if':
                     after.setdefault(pos, []).append('  !!! invalid #if\n')
                 if skipping is not None:
                     after.setdefault(pos, []).append('  !!! nested #if\n')
                 skipping = not self._hghave(lsplit[1:])
                 after.setdefault(pos, []).append(l)
             elif l.startswith('#else'):
                 if skipping is None:
                     after.setdefault(pos, []).append('  !!! missing #if\n')
                 skipping = not skipping
                 after.setdefault(pos, []).append(l)
             elif l.startswith('#endif'):
                 if skipping is None:
                     after.setdefault(pos, []).append('  !!! missing #if\n')
                 skipping = None
                 after.setdefault(pos, []).append(l)
             elif skipping:
                 after.setdefault(pos, []).append(l)
             elif l.startswith('  >>> '): # python inlines
                 after.setdefault(pos, []).append(l)
                 prepos = pos
                 pos = n
                 if not inpython:
                     # We've just entered a Python block. Add the header.
                     inpython = True
                     addsalt(prepos, False) # Make sure we report the exit code.
                     script.append('%s -m heredoctest <<EOF\n' % PYTHON)
                 addsalt(n, True)
                 script.append(l[2:])
             elif l.startswith('  ... '): # python inlines
                 after.setdefault(prepos, []).append(l)
                 script.append(l[2:])
             elif l.startswith('  $ '): # commands
                 if inpython:
                     script.append('EOF\n')
                     inpython = False
                 after.setdefault(pos, []).append(l)
                 prepos = pos
                 pos = n
                 addsalt(n, False)
                 cmd = l[4:].split()
                 if len(cmd) == 2 and cmd[0] == 'cd':
                     l = '  $ cd %s || exit 1\n' % cmd[1]
                 script.append(l[4:])
             elif l.startswith('  > '): # continuations
                 after.setdefault(prepos, []).append(l)
                 script.append(l[4:])
             elif l.startswith('  '): # results
                 # Queue up a list of expected results.
                 expected.setdefault(pos, []).append(l[2:])
             else:
                 if inpython:
                     script.append('EOF\n')
                     inpython = False
                 # Non-command/result. Queue up for merged output.
                 after.setdefault(pos, []).append(l)
 
         if inpython:
             script.append('EOF\n')
         if skipping is not None:
             after.setdefault(pos, []).append('  !!! missing #endif\n')
         addsalt(n + 1, False)
 
         return salt, script, after, expected
 
     def _processoutput(self, exitcode, output, salt, after, expected):
         # Merge the script output back into a unified test.
         warnonly = 1 # 1: not yet; 2: yes; 3: for sure not
         if exitcode != 0:
             warnonly = 3
 
         pos = -1
         postout = []
         for l in output:
             lout, lcmd = l, None
             if salt in l:
                 lout, lcmd = l.split(salt, 1)
 
             if lout:
                 if not lout.endswith('\n'):
                     lout += ' (no-eol)\n'
 
                 # Find the expected output at the current position.
                 el = None
                 if expected.get(pos, None):
                     el = expected[pos].pop(0)
 
                 r = TTest.linematch(el, lout)
                 if isinstance(r, str):
                     if r == '+glob':
                         lout = el[:-1] + ' (glob)\n'
                         r = '' # Warn only this line.
                     elif r == '-glob':
                         lout = ''.join(el.rsplit(' (glob)', 1))
                         r = '' # Warn only this line.
                     else:
                         log('\ninfo, unknown linematch result: %r\n' % r)
                         r = False
                 if r:
                     postout.append('  ' + el)
                 else:
                     if self.NEEDESCAPE(lout):
                         lout = TTest.stringescape('%s (esc)\n' %
                                                   lout.rstrip('\n'))
                     postout.append('  ' + lout) # Let diff deal with it.
                     if r != '': # If line failed.
                         warnonly = 3 # for sure not
                     elif warnonly == 1: # Is "not yet" and line is warn only.
                         warnonly = 2 # Yes do warn.
 
             if lcmd:
                 # Add on last return code.
                 ret = int(lcmd.split()[1])
                 if ret != 0:
                     postout.append('  [%s]\n' % ret)
                 if pos in after:
                     # Merge in non-active test bits.
                     postout += after.pop(pos)
                 pos = int(lcmd.split()[0])
 
         if pos in after:
             postout += after.pop(pos)
 
         if warnonly == 2:
             exitcode = False # Set exitcode to warned.
 
         return exitcode, postout
 
     @staticmethod
     def rematch(el, l):
         try:
             # use \Z to ensure that the regex matches to the end of the string
             if os.name == 'nt':
                 return re.match(el + r'\r?\n\Z', l)
             return re.match(el + r'\n\Z', l)
         except re.error:
             # el is an invalid regex
             return False
 
     @staticmethod
     def globmatch(el, l):
         # The only supported special characters are * and ? plus / which also
         # matches \ on windows. Escaping of these characters is supported.
         if el + '\n' == l:
             if os.altsep:
                 # matching on "/" is not needed for this line
                 return '-glob'
             return True
         i, n = 0, len(el)
         res = ''
         while i < n:
             c = el[i]
             i += 1
             if c == '\\' and el[i] in '*?\\/':
                 res += el[i - 1:i + 1]
                 i += 1
             elif c == '*':
                 res += '.*'
             elif c == '?':
                 res += '.'
             elif c == '/' and os.altsep:
                 res += '[/\\\\]'
             else:
                 res += re.escape(c)
         return TTest.rematch(res, l)
 
     @staticmethod
     def linematch(el, l):
         if el == l: # perfect match (fast)
             return True
         if el:
             if el.endswith(" (esc)\n"):
                 el = el[:-7].decode('string-escape') + '\n'
             if el == l or os.name == 'nt' and el[:-1] + '\r\n' == l:
                 return True
             if el.endswith(" (re)\n"):
                 return TTest.rematch(el[:-6], l)
             if el.endswith(" (glob)\n"):
                 return TTest.globmatch(el[:-8], l)
             if os.altsep and l.replace('\\', '/') == el:
                 return '+glob'
         return False
 
     @staticmethod
     def parsehghaveoutput(lines):
         '''Parse hghave log lines.
 
         Return tuple of lists (missing, failed):
           * the missing/unknown features
           * the features for which existence check failed'''
         missing = []
         failed = []
         for line in lines:
             if line.startswith(TTest.SKIPPED_PREFIX):
                 line = line.splitlines()[0]
                 missing.append(line[len(TTest.SKIPPED_PREFIX):])
             elif line.startswith(TTest.FAILED_PREFIX):
                 line = line.splitlines()[0]
                 failed.append(line[len(TTest.FAILED_PREFIX):])
 
         return missing, failed
 
     @staticmethod
     def _escapef(m):
         return TTest.ESCAPEMAP[m.group(0)]
 
     @staticmethod
     def _stringescape(s):
         return TTest.ESCAPESUB(TTest._escapef, s)
 
 
 wifexited = getattr(os, "WIFEXITED", lambda x: False)
 def run(cmd, wd, replacements, env, debug=False, timeout=None):
     """Run command in a sub-process, capturing the output (stdout and stderr).
     Return a tuple (exitcode, output).  output is None in debug mode."""
     if debug:
         proc = subprocess.Popen(cmd, shell=True, cwd=wd, env=env)
         ret = proc.wait()
         return (ret, None)
 
     proc = Popen4(cmd, wd, timeout, env)
     def cleanup():
         terminate(proc)
         ret = proc.wait()
         if ret == 0:
             ret = signal.SIGTERM << 8
         killdaemons(env['DAEMON_PIDS'])
         return ret
 
     output = ''
     proc.tochild.close()
 
     try:
         output = proc.fromchild.read()
     except KeyboardInterrupt:
         vlog('# Handling keyboard interrupt')
         cleanup()
         raise
 
     ret = proc.wait()
     if wifexited(ret):
         ret = os.WEXITSTATUS(ret)
 
     if proc.timeout:
         ret = 'timeout'
 
     if ret:
         killdaemons(env['DAEMON_PIDS'])
 
     for s, r in replacements:
         output = re.sub(s, r, output)
     return ret, output.splitlines(True)
 
 iolock = threading.Lock()
 
 class SkipTest(Exception):
     """Raised to indicate that a test is to be skipped."""
 
 class IgnoreTest(Exception):
     """Raised to indicate that a test is to be ignored."""
 
 class WarnTest(Exception):
     """Raised to indicate that a test warned."""
 
 class TestResult(unittest._TextTestResult):
     """Holds results when executing via unittest."""
     # Don't worry too much about accessing the non-public _TextTestResult.
     # It is relatively common in Python testing tools.
     def __init__(self, options, *args, **kwargs):
         super(TestResult, self).__init__(*args, **kwargs)
 
         self._options = options
 
         # unittest.TestResult didn't have skipped until 2.7. We need to
         # polyfill it.
         self.skipped = []
 
         # We have a custom "ignored" result that isn't present in any Python
         # unittest implementation. It is very similar to skipped. It may make
         # sense to map it into skip some day.
         self.ignored = []
 
         # We have a custom "warned" result that isn't present in any Python
         # unittest implementation. It is very similar to failed. It may make
         # sense to map it into fail some day.
         self.warned = []
 
         self.times = []
         self._started = {}
 
     def addFailure(self, test, reason):
         self.failures.append((test, reason))
 
         if self._options.first:
             self.stop()
 
     def addError(self, *args, **kwargs):
         super(TestResult, self).addError(*args, **kwargs)
 
         if self._options.first:
             self.stop()
 
     # Polyfill.
     def addSkip(self, test, reason):
         self.skipped.append((test, reason))
 
         if self.showAll:
             self.stream.writeln('skipped %s' % reason)
         else:
             self.stream.write('s')
             self.stream.flush()
 
     def addIgnore(self, test, reason):
         self.ignored.append((test, reason))
 
         if self.showAll:
             self.stream.writeln('ignored %s' % reason)
         else:
             self.stream.write('i')
             self.stream.flush()
 
     def addWarn(self, test, reason):
         self.warned.append((test, reason))
 
         if self._options.first:
             self.stop()
 
         if self.showAll:
             self.stream.writeln('warned %s' % reason)
         else:
             self.stream.write('~')
             self.stream.flush()
 
     def addOutputMismatch(self, test, ret, got, expected):
         """Record a mismatch in test output for a particular test."""
 
         if self._options.nodiff:
             return
 
         if self._options.view:
             os.system("%s %s %s" % (self._view, test.refpath, test.errpath))
         else:
             failed, lines = getdiff(expected, got,
                                     test.refpath, test.errpath)
             if failed:
                 self.addFailure(test, 'diff generation failed')
             else:
                 self.stream.write('\n')
                 for line in lines:
                     self.stream.write(line)
                 self.stream.flush()
 
         if ret or not self._options.interactive or \
             not os.path.exists(test.errpath):
             return
 
         iolock.acquire()
         print 'Accept this change? [n] ',
         answer = sys.stdin.readline().strip()
         iolock.release()
         if answer.lower() in ('y', 'yes'):
             if test.name.endswith('.t'):
                 rename(test.errpath, test.path)
             else:
                 rename(test.errpath, '%s.out' % test.path)
 
     def startTest(self, test):
         super(TestResult, self).startTest(test)
 
         self._started[test.name] = time.time()
 
     def stopTest(self, test, interrupted=False):
         super(TestResult, self).stopTest(test)
 
         self.times.append((test.name, time.time() - self._started[test.name]))
         del self._started[test.name]
 
         if interrupted:
             self.stream.writeln('INTERRUPTED: %s (after %d seconds)' % (
                 test.name, self.times[-1][1]))
 
 class TestSuite(unittest.TestSuite):
     """Custom unitest TestSuite that knows how to execute Mercurial tests."""
 
     def __init__(self, testdir, jobs=1, whitelist=None, blacklist=None,
                  retest=False, keywords=None, loop=False,
                  *args, **kwargs):
         """Create a new instance that can run tests with a configuration.
 
         testdir specifies the directory where tests are executed from. This
         is typically the ``tests`` directory from Mercurial's source
         repository.
 
         jobs specifies the number of jobs to run concurrently. Each test
         executes on its own thread. Tests actually spawn new processes, so
         state mutation should not be an issue.
 
         whitelist and blacklist denote tests that have been whitelisted and
         blacklisted, respectively. These arguments don't belong in TestSuite.
         Instead, whitelist and blacklist should be handled by the thing that
         populates the TestSuite with tests. They are present to preserve
         backwards compatible behavior which reports skipped tests as part
         of the results.
 
         retest denotes whether to retest failed tests. This arguably belongs
         outside of TestSuite.
 
         keywords denotes key words that will be used to filter which tests
         to execute. This arguably belongs outside of TestSuite.
 
         loop denotes whether to loop over tests forever.
         """
         super(TestSuite, self).__init__(*args, **kwargs)
 
         self._jobs = jobs
         self._whitelist = whitelist
         self._blacklist = blacklist
         self._retest = retest
         self._keywords = keywords
         self._loop = loop
 
     def run(self, result):
         # We have a number of filters that need to be applied. We do this
         # here instead of inside Test because it makes the running logic for
         # Test simpler.
         tests = []
         for test in self._tests:
             if not os.path.exists(test.path):
                 result.addSkip(test, "Doesn't exist")
                 continue
 
             if not (self._whitelist and test.name in self._whitelist):
                 if self._blacklist and test.name in self._blacklist:
                     result.addSkip(test, 'blacklisted')
                     continue
 
                 if self._retest and not os.path.exists(test.errpath):
                     result.addIgnore(test, 'not retesting')
                     continue
 
                 if self._keywords:
                     f = open(test.path)
                     t = f.read().lower() + test.name.lower()
                     f.close()
                     ignored = False
                     for k in self._keywords.lower().split():
                         if k not in t:
                             result.addIgnore(test, "doesn't match keyword")
                             ignored = True
                             break
 
                     if ignored:
                         continue
 
             tests.append(test)
 
         runtests = list(tests)
         done = queue.Queue()
         running = 0
 
         def job(test, result):
             try:
                 test(result)
                 done.put(None)
             except KeyboardInterrupt:
                 pass
             except: # re-raises
                 done.put(('!', test, 'run-test raised an error, see traceback'))
                 raise
 
         try:
             while tests or running:
                 if not done.empty() or running == self._jobs or not tests:
                     try:
                         done.get(True, 1)
                         if result and result.shouldStop:
                             break
                     except queue.Empty:
                         continue
                     running -= 1
                 if tests and not running == self._jobs:
                     test = tests.pop(0)
                     if self._loop:
                         tests.append(test)
                     t = threading.Thread(target=job, name=test.name,
                                          args=(test, result))
                     t.start()
                     running += 1
         except KeyboardInterrupt:
             for test in runtests:
                 test.abort()
 
         return result
 
 class TextTestRunner(unittest.TextTestRunner):
     """Custom unittest test runner that uses appropriate settings."""
 
     def __init__(self, runner, *args, **kwargs):
         super(TextTestRunner, self).__init__(*args, **kwargs)
 
         self._runner = runner
 
     def run(self, test):
         result = TestResult(self._runner.options, self.stream,
                             self.descriptions, self.verbosity)
 
         test(result)
 
         failed = len(result.failures)
         warned = len(result.warned)
         skipped = len(result.skipped)
         ignored = len(result.ignored)
 
         self.stream.writeln('')
 
         if not self._runner.options.noskips:
             for test, msg in result.skipped:
                 self.stream.writeln('Skipped %s: %s' % (test.name, msg))
         for test, msg in result.warned:
             self.stream.writeln('Warned %s: %s' % (test.name, msg))
         for test, msg in result.failures:
             self.stream.writeln('Failed %s: %s' % (test.name, msg))
         for test, msg in result.errors:
             self.stream.writeln('Errored %s: %s' % (test.name, msg))
 
         self._runner._checkhglib('Tested')
 
         # This differs from unittest's default output in that we don't count
         # skipped and ignored tests as part of the total test count.
         self.stream.writeln('# Ran %d tests, %d skipped, %d warned, %d failed.'
             % (result.testsRun - skipped - ignored,
                skipped + ignored, warned, failed))
         if failed:
             self.stream.writeln('python hash seed: %s' %
                 os.environ['PYTHONHASHSEED'])
         if self._runner.options.time:
             self.printtimes(result.times)
 
     def printtimes(self, times):
         self.stream.writeln('# Producing time report')
         times.sort(key=lambda t: (t[1], t[0]), reverse=True)
         cols = '%7.3f   %s'
         self.stream.writeln('%-7s   %s' % ('Time', 'Test'))
         for test, timetaken in times:
             self.stream.writeln(cols % (timetaken, test))
 
 class TestRunner(object):
     """Holds context for executing tests.
 
     Tests rely on a lot of state. This object holds it for them.
     """
 
+    # Programs required to run tests.
     REQUIREDTOOLS = [
         os.path.basename(sys.executable),
         'diff',
         'grep',
         'unzip',
         'gunzip',
         'bunzip2',
         'sed',
     ]
 
+    # Maps file extensions to test class.
     TESTTYPES = [
         ('.py', PythonTest),
         ('.t', TTest),
     ]
 
     def __init__(self):
         self.options = None
         self._testdir = None
         self._hgtmp = None
         self._installdir = None
         self._bindir = None
         self._tmpbinddir = None
         self._pythondir = None
         self._coveragefile = None
         self._createdfiles = []
         self._hgpath = None
 
     def run(self, args, parser=None):
         """Run the test suite."""
         oldmask = os.umask(022)
         try:
             parser = parser or getparser()
             options, args = parseargs(args, parser)
             self.options = options
 
             self._checktools()
             tests = self.findtests(args)
             return self._run(tests)
         finally:
             os.umask(oldmask)
 
     def _run(self, tests):
         if self.options.random:
             random.shuffle(tests)
         else:
             # keywords for slow tests
             slow = 'svn gendoc check-code-hg'.split()
             def sortkey(f):
                 # run largest tests first, as they tend to take the longest
                 try:
                     val = -os.stat(f).st_size
                 except OSError, e:
                     if e.errno != errno.ENOENT:
                         raise
                     return -1e9 # file does not exist, tell early
                 for kw in slow:
                     if kw in f:
                         val *= 10
                 return val
             tests.sort(key=sortkey)
 
         self._testdir = os.environ['TESTDIR'] = os.getcwd()
 
         if 'PYTHONHASHSEED' not in os.environ:
             # use a random python hash seed all the time
             # we do the randomness ourself to know what seed is used
             os.environ['PYTHONHASHSEED'] = str(random.getrandbits(32))
 
         if self.options.tmpdir:
             self.options.keep_tmpdir = True
             tmpdir = self.options.tmpdir
             if os.path.exists(tmpdir):
                 # Meaning of tmpdir has changed since 1.3: we used to create
                 # HGTMP inside tmpdir; now HGTMP is tmpdir.  So fail if
                 # tmpdir already exists.
                 print "error: temp dir %r already exists" % tmpdir
                 return 1
 
                 # Automatically removing tmpdir sounds convenient, but could
                 # really annoy anyone in the habit of using "--tmpdir=/tmp"
                 # or "--tmpdir=$HOME".
                 #vlog("# Removing temp dir", tmpdir)
                 #shutil.rmtree(tmpdir)
             os.makedirs(tmpdir)
         else:
             d = None
             if os.name == 'nt':
                 # without this, we get the default temp dir location, but
                 # in all lowercase, which causes troubles with paths (issue3490)
                 d = os.getenv('TMP')
             tmpdir = tempfile.mkdtemp('', 'hgtests.', d)
         self._hgtmp = os.environ['HGTMP'] = os.path.realpath(tmpdir)
 
         if self.options.with_hg:
             self._installdir = None
             self._bindir = os.path.dirname(os.path.realpath(
                                            self.options.with_hg))
             self._tmpbindir = os.path.join(self._hgtmp, 'install', 'bin')
             os.makedirs(self._tmpbindir)
 
             # This looks redundant with how Python initializes sys.path from
             # the location of the script being executed.  Needed because the
             # "hg" specified by --with-hg is not the only Python script
             # executed in the test suite that needs to import 'mercurial'
             # ... which means it's not really redundant at all.
             self._pythondir = self._bindir
         else:
             self._installdir = os.path.join(self._hgtmp, "install")
             self._bindir = os.environ["BINDIR"] = \
                 os.path.join(self._installdir, "bin")
             self._tmpbindir = self._bindir
             self._pythondir = os.path.join(self._installdir, "lib", "python")
 
         os.environ["BINDIR"] = self._bindir
         os.environ["PYTHON"] = PYTHON
 
         path = [self._bindir] + os.environ["PATH"].split(os.pathsep)
         if self._tmpbindir != self._bindir:
             path = [self._tmpbindir] + path
         os.environ["PATH"] = os.pathsep.join(path)
 
         # Include TESTDIR in PYTHONPATH so that out-of-tree extensions
         # can run .../tests/run-tests.py test-foo where test-foo
         # adds an extension to HGRC. Also include run-test.py directory to
         # import modules like heredoctest.
         pypath = [self._pythondir, self._testdir,
                   os.path.abspath(os.path.dirname(__file__))]
         # We have to augment PYTHONPATH, rather than simply replacing
         # it, in case external libraries are only available via current
         # PYTHONPATH.  (In particular, the Subversion bindings on OS X
         # are in /opt/subversion.)
         oldpypath = os.environ.get(IMPL_PATH)
         if oldpypath:
             pypath.append(oldpypath)
         os.environ[IMPL_PATH] = os.pathsep.join(pypath)
 
         self._coveragefile = os.path.join(self._testdir, '.coverage')
 
         vlog("# Using TESTDIR", self._testdir)
         vlog("# Using HGTMP", self._hgtmp)
         vlog("# Using PATH", os.environ["PATH"])
         vlog("# Using", IMPL_PATH, os.environ[IMPL_PATH])
 
         try:
             return self._runtests(tests) or 0
         finally:
             time.sleep(.1)
             self._cleanup()
 
     def findtests(self, args):
         """Finds possible test files from arguments.
 
         If you wish to inject custom tests into the test harness, this would
         be a good function to monkeypatch or override in a derived class.
         """
         if not args:
             if self.options.changed:
                 proc = Popen4('hg st --rev "%s" -man0 .' %
                               self.options.changed, None, 0)
                 stdout, stderr = proc.communicate()
                 args = stdout.strip('\0').split('\0')
             else:
                 args = os.listdir('.')
 
         return [t for t in args
                 if os.path.basename(t).startswith('test-')
                     and (t.endswith('.py') or t.endswith('.t'))]
 
     def _runtests(self, tests):
         try:
             if self._installdir:
                 self._installhg()
                 self._checkhglib("Testing")
             else:
                 self._usecorrectpython()
 
             if self.options.restart:
                 orig = list(tests)
                 while tests:
                     if os.path.exists(tests[0] + ".err"):
                         break
                     tests.pop(0)
                 if not tests:
                     print "running all tests"
                     tests = orig
 
             tests = [self._gettest(t, i) for i, t in enumerate(tests)]
 
             failed = False
             warned = False
 
             suite = TestSuite(self._testdir,
                               jobs=self.options.jobs,
                               whitelist=self.options.whitelisted,
                               blacklist=self.options.blacklist,
                               retest=self.options.retest,
                               keywords=self.options.keywords,
                               loop=self.options.loop,
                               tests=tests)
             verbosity = 1
             if self.options.verbose:
                 verbosity = 2
             runner = TextTestRunner(self, verbosity=verbosity)
             runner.run(suite)
 
             if self.options.anycoverage:
                 self._outputcoverage()
         except KeyboardInterrupt:
             failed = True
             print "\ninterrupted!"
 
         if failed:
             return 1
         if warned:
             return 80
 
     def _gettest(self, test, count):
         """Obtain a Test by looking at its filename.
 
         Returns a Test instance. The Test may not be runnable if it doesn't
         map to a known type.
         """
         lctest = test.lower()
         testcls = Test
 
         for ext, cls in self.TESTTYPES:
             if lctest.endswith(ext):
                 testcls = cls
                 break
 
         refpath = os.path.join(self._testdir, test)
         tmpdir = os.path.join(self._hgtmp, 'child%d' % count)
 
         return testcls(refpath, tmpdir,
                        keeptmpdir=self.options.keep_tmpdir,
                        debug=self.options.debug,
                        timeout=self.options.timeout,
                        startport=self.options.port + count * 3,
                        extraconfigopts=self.options.extra_config_opt,
                        py3kwarnings=self.options.py3k_warnings,
                        shell=self.options.shell)
 
     def _cleanup(self):
         """Clean up state from this test invocation."""
 
         if self.options.keep_tmpdir:
             return
 
         vlog("# Cleaning up HGTMP", self._hgtmp)
         shutil.rmtree(self._hgtmp, True)
         for f in self._createdfiles:
             try:
                 os.remove(f)
             except OSError:
                 pass
 
     def _usecorrectpython(self):
-        # Some tests run the Python interpreter. They must use the
-        # same interpreter or bad things will happen.
+        """Configure the environment to use the appropriate Python in tests."""
+        # Tests must use the same interpreter as us or bad things will happen.
         pyexename = sys.platform == 'win32' and 'python.exe' or 'python'
         if getattr(os, 'symlink', None):
             vlog("# Making python executable in test path a symlink to '%s'" %
                  sys.executable)
             mypython = os.path.join(self._tmpbindir, pyexename)
             try:
                 if os.readlink(mypython) == sys.executable:
                     return
                 os.unlink(mypython)
             except OSError, err:
                 if err.errno != errno.ENOENT:
                     raise
             if self._findprogram(pyexename) != sys.executable:
                 try:
                     os.symlink(sys.executable, mypython)
                     self._createdfiles.append(mypython)
                 except OSError, err:
                     # child processes may race, which is harmless
                     if err.errno != errno.EEXIST:
                         raise
         else:
             exedir, exename = os.path.split(sys.executable)
             vlog("# Modifying search path to find %s as %s in '%s'" %
                  (exename, pyexename, exedir))
             path = os.environ['PATH'].split(os.pathsep)
             while exedir in path:
                 path.remove(exedir)
             os.environ['PATH'] = os.pathsep.join([exedir] + path)
             if not self._findprogram(pyexename):
                 print "WARNING: Cannot find %s in search path" % pyexename
 
     def _installhg(self):
+        """Install hg into the test environment.
+
+        This will also configure hg with the appropriate testing settings.
+        """
         vlog("# Performing temporary installation of HG")
         installerrs = os.path.join("tests", "install.err")
         compiler = ''
         if self.options.compiler:
             compiler = '--compiler ' + self.options.compiler
         pure = self.options.pure and "--pure" or ""
         py3 = ''
         if sys.version_info[0] == 3:
             py3 = '--c2to3'
 
         # Run installer in hg root
         script = os.path.realpath(sys.argv[0])
         hgroot = os.path.dirname(os.path.dirname(script))
         os.chdir(hgroot)
         nohome = '--home=""'
         if os.name == 'nt':
             # The --home="" trick works only on OS where os.sep == '/'
             # because of a distutils convert_path() fast-path. Avoid it at
             # least on Windows for now, deal with .pydistutils.cfg bugs
             # when they happen.
             nohome = ''
         cmd = ('%(exe)s setup.py %(py3)s %(pure)s clean --all'
                ' build %(compiler)s --build-base="%(base)s"'
                ' install --force --prefix="%(prefix)s"'
                ' --install-lib="%(libdir)s"'
                ' --install-scripts="%(bindir)s" %(nohome)s >%(logfile)s 2>&1'
                % {'exe': sys.executable, 'py3': py3, 'pure': pure,
                   'compiler': compiler,
                   'base': os.path.join(self._hgtmp, "build"),
                   'prefix': self._installdir, 'libdir': self._pythondir,
                   'bindir': self._bindir,
                   'nohome': nohome, 'logfile': installerrs})
         vlog("# Running", cmd)
         if os.system(cmd) == 0:
             if not self.options.verbose:
                 os.remove(installerrs)
         else:
             f = open(installerrs)
             for line in f:
                 print line,
             f.close()
             sys.exit(1)
         os.chdir(self._testdir)
 
         self._usecorrectpython()
 
         if self.options.py3k_warnings and not self.options.anycoverage:
             vlog("# Updating hg command to enable Py3k Warnings switch")
             f = open(os.path.join(self._bindir, 'hg'), 'r')
             lines = [line.rstrip() for line in f]
             lines[0] += ' -3'
             f.close()
             f = open(os.path.join(self._bindir, 'hg'), 'w')
             for line in lines:
                 f.write(line + '\n')
             f.close()
 
         hgbat = os.path.join(self._bindir, 'hg.bat')
         if os.path.isfile(hgbat):
             # hg.bat expects to be put in bin/scripts while run-tests.py
             # installation layout put it in bin/ directly. Fix it
             f = open(hgbat, 'rb')
             data = f.read()
             f.close()
             if '"%~dp0..\python" "%~dp0hg" %*' in data:
                 data = data.replace('"%~dp0..\python" "%~dp0hg" %*',
                                     '"%~dp0python" "%~dp0hg" %*')
                 f = open(hgbat, 'wb')
                 f.write(data)
                 f.close()
             else:
                 print 'WARNING: cannot fix hg.bat reference to python.exe'
 
         if self.options.anycoverage:
             custom = os.path.join(self._testdir, 'sitecustomize.py')
             target = os.path.join(self._pythondir, 'sitecustomize.py')
             vlog('# Installing coverage trigger to %s' % target)
             shutil.copyfile(custom, target)
             rc = os.path.join(self._testdir, '.coveragerc')
             vlog('# Installing coverage rc to %s' % rc)
             os.environ['COVERAGE_PROCESS_START'] = rc
             fn = os.path.join(self._installdir, '..', '.coverage')
             os.environ['COVERAGE_FILE'] = fn
 
     def _checkhglib(self, verb):
         """Ensure that the 'mercurial' package imported by python is
         the one we expect it to be.  If not, print a warning to stderr."""
         expecthg = os.path.join(self._pythondir, 'mercurial')
         actualhg = self._gethgpath()
         if os.path.abspath(actualhg) != os.path.abspath(expecthg):
             sys.stderr.write('warning: %s with unexpected mercurial lib: %s\n'
                              '         (expected %s)\n'
                              % (verb, actualhg, expecthg))
     def _gethgpath(self):
         """Return the path to the mercurial package that is actually found by
         the current Python interpreter."""
         if self._hgpath is not None:
             return self._hgpath
 
         cmd = '%s -c "import mercurial; print (mercurial.__path__[0])"'
         pipe = os.popen(cmd % PYTHON)
         try:
             self._hgpath = pipe.read().strip()
         finally:
             pipe.close()
 
         return self._hgpath
 
     def _outputcoverage(self):
+        """Produce code coverage output."""
         vlog('# Producing coverage report')
         os.chdir(self._pythondir)
 
         def covrun(*args):
             cmd = 'coverage %s' % ' '.join(args)
             vlog('# Running: %s' % cmd)
             os.system(cmd)
 
         covrun('-c')
         omit = ','.join(os.path.join(x, '*') for x in
                         [self._bindir, self._testdir])
         covrun('-i', '-r', '"--omit=%s"' % omit) # report
         if self.options.htmlcov:
             htmldir = os.path.join(self._testdir, 'htmlcov')
             covrun('-i', '-b', '"--directory=%s"' % htmldir,
                    '"--omit=%s"' % omit)
         if self.options.annotate:
             adir = os.path.join(self._testdir, 'annotated')
             if not os.path.isdir(adir):
                 os.mkdir(adir)
             covrun('-i', '-a', '"--directory=%s"' % adir, '"--omit=%s"' % omit)
 
     def _findprogram(self, program):
         """Search PATH for a executable program"""
         for p in os.environ.get('PATH', os.defpath).split(os.pathsep):
             name = os.path.join(p, program)
             if os.name == 'nt' or os.access(name, os.X_OK):
                 return name
         return None
 
     def _checktools(self):
-        # Before we go any further, check for pre-requisite tools
-        # stuff from coreutils (cat, rm, etc) are not tested
+        """Ensure tools required to run tests are present."""
         for p in self.REQUIREDTOOLS:
             if os.name == 'nt' and not p.endswith('.exe'):
                 p += '.exe'
             found = self._findprogram(p)
             if found:
                 vlog("# Found prerequisite", p, "at", found)
             else:
                 print "WARNING: Did not find prerequisite tool: %s " % p
 
 if __name__ == '__main__':
     runner = TestRunner()
     sys.exit(runner.run(sys.argv[1:]))