Issue 10242. Switching unittest.TestCase.assertItemsEqual to use a collections.Counter under the hood.
This fixes bugs when comparing collections of items like sets that can be sorted without raising an exception but where sorting has no meaning.
diff --git a/Lib/unittest/case.py b/Lib/unittest/case.py
index 33ab47a..cd8f4fa 100644
--- a/Lib/unittest/case.py
+++ b/Lib/unittest/case.py
@@ -1,5 +1,6 @@
"""Test case implementation"""
+import collections
import sys
import functools
import difflib
@@ -850,14 +851,12 @@
self.fail(self._formatMessage(msg, standardMsg))
def assertItemsEqual(self, expected_seq, actual_seq, msg=None):
- """An unordered sequence / set specific comparison. It asserts that
- expected_seq and actual_seq contain the same elements. It is
- the equivalent of::
+ """An unordered sequence specific comparison. It asserts that
+ actual_seq and expected_seq have the same element counts.
+ Equivalent to::
- self.assertEqual(sorted(expected_seq), sorted(actual_seq))
-
- Raises with an error message listing which elements of expected_seq
- are missing from actual_seq and vice versa if any.
+ self.assertEqual(Counter(iter(actual_seq)),
+ Counter(iter(expected_seq)))
Asserts that each element has the same count in both sequences.
Example:
@@ -872,17 +871,18 @@
"comparing unequal types"]:
warnings.filterwarnings("ignore", _msg, DeprecationWarning)
try:
- expected = sorted(expected_seq)
- actual = sorted(actual_seq)
+ actual = collections.Counter(iter(actual_seq))
+ expected = collections.Counter(iter(expected_seq))
except TypeError:
# Unsortable items (example: set(), complex(), ...)
- expected = list(expected_seq)
actual = list(actual_seq)
- missing, unexpected = unorderable_list_difference(
- expected, actual, ignore_duplicate=False
- )
+ expected = list(expected_seq)
+ missing, unexpected = unorderable_list_difference(expected, actual)
else:
- return self.assertSequenceEqual(expected, actual, msg=msg)
+ if actual == expected:
+ return
+ missing = list(expected - actual)
+ unexpected = list(actual - expected)
errors = []
if missing:
diff --git a/Lib/unittest/test/test_case.py b/Lib/unittest/test/test_case.py
index c42d98d..250e905 100644
--- a/Lib/unittest/test/test_case.py
+++ b/Lib/unittest/test/test_case.py
@@ -711,6 +711,11 @@
self.assertRaises(self.failureException, self.assertItemsEqual,
[1, {'b': 2}, None, True], [{'b': 2}, True, None])
+ # Same elements which don't reliably compare, in
+ # different order, see issue 10242
+ a = [{2,4}, {1,2}]
+ b = a[::-1]
+ self.assertItemsEqual(a, b)
def testAssertSetEqual(self):
set1 = set()
diff --git a/Misc/NEWS b/Misc/NEWS
index b1b0265..dc80eb8 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -22,6 +22,9 @@
Library
-------
+- Issue #10242: unittest.TestCase.assertItemsEqual makes too many assumgptions
+ about input.
+
- Issue #10611: SystemExit should not cause a unittest test run to exit.
- Issue #6791: Limit header line length (to 65535 bytes) in http.client,