The doctest module fails when the expected result
string has non-ascii charcaters even if the # -*-
coding: XXX -*- line is properly set.

The enclosed code sample produce the following error:

Traceback (most recent call last):
  File "test_iso-8859-15.py", line 41, in ?
    _test()
  File "test_iso-8859-15.py", line 26, in _test
    tried, failed = runner.run(t)
  File "/usr/lib/python2.4/doctest.py", line 1376, in run
    return self.__run(test, compileflags, out)
  File "/usr/lib/python2.4/doctest.py", line 1259, in __run
    if check(example.want, got, self.optionflags):
  File "/usr/lib/python2.4/doctest.py", line 1475, in
check_output
    if got == want:
UnicodeDecodeError: 'ascii' codec can't decode byte
0xe9 in position 8: ordinal not in range(128)

Logged In: YES 
user_id=31435

Please try the patch at

http://www.python.org/sf/1080727

and report back on whether it solves your problem (attaching 
comments to the patch report would be most useful).

Logged In: YES 
user_id=795041

Unfortunateny that patch does not fix my problem. The patch
at bug #1080727 fixes the problem for doctests written in
external reST files (testfile and DocFileTest functions). My
problem is related to internal docstring encoding (testmod
for instance). However, Bjorn Tillenius says:
"""
If one writes doctests within documentation strings of
classes and
functions, it's possible to use non-ASCII characters since
one can
specify the encoding used in the source file.
"""
So according to him, docstrings' doctests with non-ascii
characters should work by default. So maybe my system setup
is somewhat broken. Could somebody please confirm/infirm
this by running the attached sample script on his system?

My system config:
LANG=fr_FR@euro (on linux)
python 2.4.1 with:  sys.getdefaultencoding() == 'ascii' 
and locale.getpreferredencoding() == 'ISO-8859-15'
$ file test_iso-8859-15.py
test_iso-8859-15.py: ISO-8859 English text

Logged In: YES 
user_id=1032069

I'm quite sure that you can use non-ASCII characters in 
your doctest, given that it's a unicode string. So if you 
make your docstring a unicode string, it should work. That 
is:

u"""Docstring containing non-ASCII characters.
...
"""

Logged In: YES 
user_id=31435

Unassigned myself -- don't know enough about encodings.

I made some tests with Python 2.5 on an Ubuntu Edgy system with an UTF-8 terminal. Here's the basic test which does work correctly:

# -*- encoding: utf-8 -*-
__doc__ = u"""
>>> print u'ä'
ä
""" ; import doctest ; doctest.testmod()

If I start to vary the "ä" (a with umlaut) characters in "print u'ä'" (the test) and the "ä" below it (expected result), I get a UnicodeEncodeError whenever doctest tries to print a message about non-matching test output.

Here's a summary of my results in the format of
test | expected result | success/failure
Note that \u00e4 is unicode for the "ä" character.

ä      | ä      | success
\u00e4 | ä      | success
ä      | \u00e4 | success
\u00e4 | \u00e4 | success
ä      | x      | fails to display message
x      | ä      | fails to display message
\u00e4 | x      | fails to display message
x      | \u00e4 | fails to display message

Conclusion: test running and output checking do work correctly, but there's a problem displaying messages about non-matching output whenever either the expected output or the output produced by the test contain any extended characters.

The doctest documentation doesn't give any hint on work-arounds.

I have confirmed everything that akaihola reports in Python 2.4, 2.5 and
2.6, but the problem is not limited to non-matching test output. It also
happens with doctests with zero failures when the module is run with the
-v command-line switch, or testmod is called with verbose=True.

The attached file shows a work-around: handle the UnicodeEncodeError
thrown by testmod, and display the "object" attribute of the exception
to see exactly where the problem is.

See attached patch which works for error reporting and verbose output.

My last patch only changed the encoding used in DocTestRunner.run().
This new patch will apply the same to DocTestCase.runTest().

Here is some more information.

--- snip ---

Normal behaviour
================

$ locale
LANG=en_US.UTF-8
LC_CTYPE=en_US.UTF-8
LC_NUMERIC=POSIX
LC_TIME=en_GB.UTF-8
LC_COLLATE=en_GB.UTF-8
LC_MONETARY=de_DE.UTF-8
LC_MESSAGES=en_US.UTF-8
LC_PAPER=de_DE.UTF-8
LC_NAME=en_US.UTF-8
LC_ADDRESS=de_DE.UTF-8
LC_TELEPHONE=de_DE.UTF-8
LC_MEASUREMENT=de_DE.UTF-8
LC_IDENTIFICATION=de_DE.UTF-8
LC_ALL=
$ python2.6
Python 2.6.3 (r263:75183, Oct  6 2009, 17:19:56) 
[GCC 4.3.4] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> print '缺陷'
缺陷
>>> print u'缺陷'
缺陷
>>> '缺陷'
'\xe7\xbc\xba\xe9\x99\xb7'
>>> u'缺陷'
u'\u7f3a\u9677'
>>> '缺陷'.decode('utf8')
u'\u7f3a\u9677'
>>> u'\u7f3a\u9677'
u'\u7f3a\u9677'
>>> 
$ cat unicode_bug.py 
#!/usr/bin/env python
# -*- coding: UTF-8 -*-

def print_string():
    """
    >>> print '缺陷'
    缺陷
    """
    pass

def print_unicode():
    """
    >>> print u'缺陷'
    缺陷
    """
    pass

def string_repr():
    """
    >>> '缺陷'
    '\xe7\xbc\xba\xe9\x99\xb7'
    """
    pass

def unicode_repr():
    """
    >>> u'缺陷'
    u'\u7f3a\u9677'
    """
    pass

def decode():
    """
    >>> '缺陷'.decode('utf8')
    u'\u7f3a\u9677'
    """
    pass

def unicode_escape_repr():
    """
    >>> u'\u7f3a\u9677'
    u'\u7f3a\u9677'
    """
    pass

if __name__ == "__main__":
    import doctest
    doctest.testmod()

$ python2.5 unicode_bug.py 
/usr/lib/python2.5/doctest.py:1460: UnicodeWarning: Unicode equal
comparison failed to convert both arguments to Unicode - interpreting
them as being unequal
  if got == want:
/usr/lib/python2.5/doctest.py:1480: UnicodeWarning: Unicode equal
comparison failed to convert both arguments to Unicode - interpreting
them as being unequal
  if got == want:
Traceback (most recent call last):
  File "unicode_bug.py", line 48, in <module>
    doctest.testmod()
  File "/usr/lib/python2.5/doctest.py", line 1815, in testmod
    runner.run(test)
  File "/usr/lib/python2.5/doctest.py", line 1361, in run
    return self.__run(test, compileflags, out)
  File "/usr/lib/python2.5/doctest.py", line 1277, in __run
    self.report_failure(out, test, example, got)
  File "/usr/lib/python2.5/doctest.py", line 1141, in report_failure
    self._checker.output_difference(example, got, self.optionflags))
  File "/usr/lib/python2.5/doctest.py", line 1565, in output_difference
    return 'Expected:\n%sGot:\n%s' % (_indent(want), _indent(got))
UnicodeDecodeError: 'ascii' codec can't decode byte 0xe7 in position 14:
ordinal not in range(128)

$ python2.6 unicode_bug.py 
/usr/local/lib/python2.6/doctest.py:1475: UnicodeWarning: Unicode equal
comparison failed to convert both arguments to Unicode - interpreting
them as being unequal
  if got == want:
/usr/local/lib/python2.6/doctest.py:1495: UnicodeWarning: Unicode equal
comparison failed to convert both arguments to Unicode - interpreting
them as being unequal
  if got == want:
Traceback (most recent call last):
  File "unicode_bug.py", line 48, in <module>
    doctest.testmod()
  File "/usr/local/lib/python2.6/doctest.py", line 1830, in testmod
    runner.run(test)
  File "/usr/local/lib/python2.6/doctest.py", line 1374, in run
    return self.__run(test, compileflags, out)
  File "/usr/local/lib/python2.6/doctest.py", line 1290, in __run
    self.report_failure(out, test, example, got)
  File "/usr/local/lib/python2.6/doctest.py", line 1154, in report_failure
    self._checker.output_difference(example, got, self.optionflags))
  File "/usr/local/lib/python2.6/doctest.py", line 1580, in
output_difference
    return 'Expected:\n%sGot:\n%s' % (_indent(want), _indent(got))
UnicodeDecodeError: 'ascii' codec can't decode byte 0xe7 in position 14:
ordinal not in range(128)

$ nosetests -V
nosetests version 0.11.1

$ nosetests --with-doctest -v unicode_bug.py 
Doctest: unicode_bug.decode ... ok
Doctest: unicode_bug.print_string ... ok
Doctest: unicode_bug.print_unicode ...
/usr/local/lib/python2.6/doctest.py:1475: UnicodeWarning: Unicode equal
comparison failed to convert both arguments to Unicode - interpreting
them as being unequal
  if got == want:
/usr/local/lib/python2.6/doctest.py:1495: UnicodeWarning: Unicode equal
comparison failed to convert both arguments to Unicode - interpreting
them as being unequal
  if got == want:
ERROR
Doctest: unicode_bug.string_repr ... FAIL
Doctest: unicode_bug.unicode_escape_repr ... ok
Doctest: unicode_bug.unicode_repr ... FAIL

======================================================================
ERROR: Doctest: unicode_bug.print_unicode
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/usr/local/lib/python2.6/doctest.py", line 2140, in runTest
    test, out=new.write, clear_globs=False)
  File "/usr/local/lib/python2.6/doctest.py", line 1374, in run
    return self.__run(test, compileflags, out)
  File "/usr/local/lib/python2.6/doctest.py", line 1290, in __run
    self.report_failure(out, test, example, got)
  File "/usr/local/lib/python2.6/doctest.py", line 1154, in report_failure
    self._checker.output_difference(example, got, self.optionflags))
  File "/usr/local/lib/python2.6/doctest.py", line 1580, in
output_difference
    return 'Expected:\n%sGot:\n%s' % (_indent(want), _indent(got))
UnicodeDecodeError: 'ascii' codec can't decode byte 0xe7 in position 14:
ordinal not in range(128)

======================================================================
FAIL: Doctest: unicode_bug.string_repr
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/usr/local/lib/python2.6/doctest.py", line 2145, in runTest
    raise self.failureException(self.format_failure(new.getvalue()))
AssertionError: Failed doctest test for unicode_bug.string_repr
  File "/home/babilen/test/unicode_bug.py", line 18, in string_repr

----------------------------------------------------------------------
File "/home/babilen/test/unicode_bug.py", line 20, in
unicode_bug.string_repr
Failed example:
    '缺陷'
Expected:
    '缺陷'
Got:
    '\xe7\xbc\xba\xe9\x99\xb7'


======================================================================
FAIL: Doctest: unicode_bug.unicode_repr
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/usr/local/lib/python2.6/doctest.py", line 2145, in runTest
    raise self.failureException(self.format_failure(new.getvalue()))
AssertionError: Failed doctest test for unicode_bug.unicode_repr
  File ".../unicode_bug.py", line 25, in unicode_repr

----------------------------------------------------------------------
File ".../unicode_bug.py", line 27, in unicode_bug.unicode_repr
Failed example:
    u'缺陷'
Expected:
    u'\u7f3a\u9677'
Got:
    u'\xe7\xbc\xba\xe9\x99\xb7'


----------------------------------------------------------------------
Ran 6 tests in 0.011s

FAILED (errors=1, failures=2)

--- snip ---

unicode_literals
================

$ python2.6
Python 2.6.3 (r263:75183, Oct  6 2009, 17:19:56) 
[GCC 4.3.4] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> from __future__ import unicode_literals
>>> print '缺陷'
缺陷
>>> print u'缺陷'
缺陷
>>> '缺陷'
u'\u7f3a\u9677'
>>> u'缺陷'
u'\u7f3a\u9677'
>>> '缺陷'.decode('utf8')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/local/lib/python2.6/encodings/utf_8.py", line 16, in decode
    return codecs.utf_8_decode(input, errors, True)
UnicodeEncodeError: 'ascii' codec can't encode characters in position
0-1: ordinal not in range(128)
>>> u'\u7f3a\u9677'
u'\u7f3a\u9677'

$ cat unicode_bug_literals.py
#!/usr/bin/env python
# -*- coding: UTF-8 -*-

from __future__ import unicode_literals

def print_string():
    """
    >>> print '缺陷'
    缺陷
    """
    pass

def print_unicode():
    """
    >>> print u'缺陷'
    缺陷
    """
    pass

def string_repr():
    """
    >>> '缺陷'
    u'\u7f3a\u9677'
    """
    pass

def unicode_repr():
    """
    >>> u'缺陷'
    u'\u7f3a\u9677'
    """
    pass

def unicode_escape_repr():
    """
    >>> u'\u7f3a\u9677'
    u'\u7f3a\u9677'
    """
    pass

if __name__ == "__main__":
    import doctest
    doctest.testmod()

$ python2.6 unicode_bug_literals.py
Traceback (most recent call last):
  File "unicode_bug_literals.py", line 43, in <module>
    doctest.testmod()
  File "/usr/local/lib/python2.6/doctest.py", line 1830, in testmod
    runner.run(test)
  File "/usr/local/lib/python2.6/doctest.py", line 1374, in run
    return self.__run(test, compileflags, out)
  File "/usr/local/lib/python2.6/doctest.py", line 1290, in __run
    self.report_failure(out, test, example, got)
  File "/usr/local/lib/python2.6/doctest.py", line 1154, in report_failure
    self._checker.output_difference(example, got, self.optionflags))
UnicodeEncodeError: 'ascii' codec can't encode characters in position
157-158: ordinal not in range(128)

$ nosetests --with-doctest -v unicode_bug_literals.py 
Doctest: unicode_bug_literals.print_string ... ok
Doctest: unicode_bug_literals.print_unicode ... ok
Doctest: unicode_bug_literals.string_repr ... FAIL
Doctest: unicode_bug_literals.unicode_escape_repr ... FAIL
Doctest: unicode_bug_literals.unicode_repr ... FAIL

======================================================================
FAIL: Doctest: unicode_bug_literals.string_repr
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/usr/local/lib/python2.6/doctest.py", line 2145, in runTest
    raise self.failureException(self.format_failure(new.getvalue()))
AssertionError: <unprintable AssertionError object>

======================================================================
FAIL: Doctest: unicode_bug_literals.unicode_escape_repr
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/usr/local/lib/python2.6/doctest.py", line 2145, in runTest
    raise self.failureException(self.format_failure(new.getvalue()))
AssertionError: <unprintable AssertionError object>

======================================================================
FAIL: Doctest: unicode_bug_literals.unicode_repr
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/usr/local/lib/python2.6/doctest.py", line 2145, in runTest
    raise self.failureException(self.format_failure(new.getvalue()))
AssertionError: <unprintable AssertionError object>

----------------------------------------------------------------------
Ran 5 tests in 0.011s

FAILED (failures=3)

--- snip ---

With doctest.unicode-2.patch
============================

$ nosetests --with-doctest -v unicode_bug.py 
Doctest: unicode_bug.decode ... ok
Doctest: unicode_bug.print_string ... ok
Doctest: unicode_bug.print_unicode ...
/usr/local/lib/python2.6/doctest.py:1480: UnicodeWarning: Unicode equal
comparison failed to convert both arguments to Unicode - interpreting
them as being unequal
  if got == want:
/usr/local/lib/python2.6/doctest.py:1500: UnicodeWarning: Unicode equal
comparison failed to convert both arguments to Unicode - interpreting
them as being unequal
  if got == want:
ERROR
Doctest: unicode_bug.string_repr ... ERROR
Doctest: unicode_bug.unicode_escape_repr ... ok
Doctest: unicode_bug.unicode_repr ... ERROR

======================================================================
ERROR: Doctest: unicode_bug.print_unicode
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/usr/local/lib/python2.6/doctest.py", line 2150, in runTest
    clear_globs=False)
  File "/usr/local/lib/python2.6/doctest.py", line 1379, in run
    return self.__run(test, compileflags, out)
  File "/usr/local/lib/python2.6/doctest.py", line 1291, in __run
    self.report_failure(out, test, example, got)
  File "/usr/local/lib/python2.6/doctest.py", line 1155, in report_failure
    self._checker.output_difference(example, got, self.optionflags))
  File "/usr/local/lib/python2.6/doctest.py", line 1585, in
output_difference
    return 'Expected:\n%sGot:\n%s' % (_indent(want), _indent(got))
UnicodeDecodeError: 'ascii' codec can't decode byte 0xe7 in position 14:
ordinal not in range(128)

======================================================================
ERROR: Doctest: unicode_bug.string_repr
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/usr/local/lib/python2.6/doctest.py", line 2150, in runTest
    clear_globs=False)
  File "/usr/local/lib/python2.6/doctest.py", line 1379, in run
    return self.__run(test, compileflags, out)
  File "/usr/local/lib/python2.6/doctest.py", line 1291, in __run
    self.report_failure(out, test, example, got)
  File "/usr/local/lib/python2.6/doctest.py", line 1155, in report_failure
    self._checker.output_difference(example, got, self.optionflags))
  File "/usr/local/lib/python2.6/doctest.py", line 2149, in <lambda>
    test, out=lambda x: new.write(x.encode(output_encoding)),
UnicodeDecodeError: 'ascii' codec can't decode byte 0xe7 in position
170: ordinal not in range(128)

======================================================================
ERROR: Doctest: unicode_bug.unicode_repr
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/usr/local/lib/python2.6/doctest.py", line 2150, in runTest
    clear_globs=False)
  File "/usr/local/lib/python2.6/doctest.py", line 1379, in run
    return self.__run(test, compileflags, out)
  File "/usr/local/lib/python2.6/doctest.py", line 1291, in __run
    self.report_failure(out, test, example, got)
  File "/usr/local/lib/python2.6/doctest.py", line 1155, in report_failure
    self._checker.output_difference(example, got, self.optionflags))
  File "/usr/local/lib/python2.6/doctest.py", line 2149, in <lambda>
    test, out=lambda x: new.write(x.encode(output_encoding)),
UnicodeDecodeError: 'ascii' codec can't decode byte 0xe7 in position
172: ordinal not in range(128)

----------------------------------------------------------------------
Ran 6 tests in 0.010s

FAILED (errors=3)

$ nosetests --with-doctest -v unicode_bug_literals.py 
Doctest: unicode_bug_literals.print_string ... ok
Doctest: unicode_bug_literals.print_unicode ... ok
Doctest: unicode_bug_literals.string_repr ... FAIL
Doctest: unicode_bug_literals.unicode_escape_repr ... FAIL
Doctest: unicode_bug_literals.unicode_repr ... FAIL

======================================================================
FAIL: Doctest: unicode_bug_literals.string_repr
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/usr/local/lib/python2.6/doctest.py", line 2155, in runTest
    raise self.failureException(self.format_failure(new.getvalue()))
AssertionError: Failed doctest test for unicode_bug_literals.string_repr
  File "/home/babilen/test/unicode_bug_literals.py", line 20, in string_repr

----------------------------------------------------------------------
File "/home/babilen/test/unicode_bug_literals.py", line 22, in
unicode_bug_literals.string_repr
Failed example:
    '缺陷'
Expected:
    u'缺陷'
Got:
    u'\u7f3a\u9677'


======================================================================
FAIL: Doctest: unicode_bug_literals.unicode_escape_repr
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/usr/local/lib/python2.6/doctest.py", line 2155, in runTest
    raise self.failureException(self.format_failure(new.getvalue()))
AssertionError: Failed doctest test for
unicode_bug_literals.unicode_escape_repr
  File "/home/babilen/test/unicode_bug_literals.py", line 34, in
unicode_escape_repr

----------------------------------------------------------------------
File "/home/babilen/test/unicode_bug_literals.py", line 36, in
unicode_bug_literals.unicode_escape_repr
Failed example:
    u'缺陷'
Expected:
    u'缺陷'
Got:
    u'\u7f3a\u9677'


======================================================================
FAIL: Doctest: unicode_bug_literals.unicode_repr
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/usr/local/lib/python2.6/doctest.py", line 2155, in runTest
    raise self.failureException(self.format_failure(new.getvalue()))
AssertionError: Failed doctest test for unicode_bug_literals.unicode_repr
  File "/home/babilen/test/unicode_bug_literals.py", line 27, in
unicode_repr

----------------------------------------------------------------------
File "/home/babilen/test/unicode_bug_literals.py", line 29, in
unicode_bug_literals.unicode_repr
Failed example:
    u'缺陷'
Expected:
    u'缺陷'
Got:
    u'\u7f3a\u9677'


----------------------------------------------------------------------
Ran 5 tests in 0.009s

FAILED (failures=3)

--- snip ---

If you need further information do not hesitate to contact me.

with kind regards

    Wolodja Wentland