The attached example unit test file shows that assertDictContainsSubset cannot handle error messages that need to show integer keys. Below is the output of the test suite, where "test_mixed_keys_fail" has an error (code mistake), while "test_text_keys_fail" produces a failure (result mistake) as expected.

C:\notes>C:\Python31\python.exe test_one_and_one.py
.E.F
======================================================================
ERROR: test_mixed_keys_fail (__main__.Test_one_and_one)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "test_one_and_one.py", line 30, in test_mixed_keys_fail
    self.assertDictContainsSubset({3: "this does not exist"}, self.dict_with_mix
ed_keys)
  File "C:\python31\lib\unittest.py", line 908, in assertDictContainsSubset
    standardMsg = 'Missing: %r' % ','.join(missing)
TypeError: sequence item 0: expected str instance, int found

======================================================================
FAIL: test_text_keys_fail (__main__.Test_one_and_one)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "test_one_and_one.py", line 33, in test_text_keys_fail
    self.assertDictContainsSubset({"3": "this does not exist"}, self.dict_with_t
ext_keys)
AssertionError: Missing: '3'

----------------------------------------------------------------------
Ran 4 tests in 0.010s

FAILED (failures=1, errors=1)

Thanks for reporting this.

I can fix this particular error easily by repr'ing the keys. In the process I've found another fun way of killing this assert method:


        one = ''.join(chr(i) for i in range(255))
        two = u'\uFFFD'
        first = {'foo': one}
        second = {'foo': two}
        self.assertDictContainsSubset(first, second)

  File "/Users/michael/Dev/Packages/python-trunk/Lib/unittest/case.py", line 728, in assertDictContainsSubset
    (key, value, actual[key]))
UnicodeDecodeError: 'ascii' codec can't decode byte 0x80 in position 143: ordinal not in range(128)

Fixed in revision 78229.