The unittest.TestCase.assertEqual() now displays the differences in lists,
tuples, dicts and sets on failure.
Many new handy type and comparison specific assert* methods have been added
that fail with error messages actually useful for debugging. Contributed in
by Google and completed with help from mfoord and GvR at PyCon 2009 sprints.
Discussion lives in http://bugs.python.org/issue2578.
diff --git a/Lib/unittest.py b/Lib/unittest.py
index 10b68ed..0f2d235 100644
--- a/Lib/unittest.py
+++ b/Lib/unittest.py
@@ -14,11 +14,11 @@
class IntegerArithmenticTestCase(unittest.TestCase):
def testAdd(self): ## test method names begin 'test*'
- self.assertEquals((1 + 2), 3)
- self.assertEquals(0 + 1, 1)
+ self.assertEqual((1 + 2), 3)
+ self.assertEqual(0 + 1, 1)
def testMultiply(self):
- self.assertEquals((0 * 10), 0)
- self.assertEquals((5 * 8), 40)
+ self.assertEqual((0 * 10), 0)
+ self.assertEqual((5 * 8), 40)
if __name__ == '__main__':
unittest.main()
@@ -45,12 +45,15 @@
SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
'''
-import time
-import sys
-import traceback
-import os
-import types
+import difflib
import functools
+import os
+import pprint
+import re
+import sys
+import time
+import traceback
+import types
##############################################################################
# Exported classes and functions
@@ -251,11 +254,13 @@
len(self.failures))
-class AssertRaisesContext(object):
+class _AssertRaisesContext(object):
+ """A context manager used to implement TestCase.assertRaises* methods."""
- def __init__(self, expected, test_case):
+ def __init__(self, expected, test_case, expected_regexp=None):
self.expected = expected
self.failureException = test_case.failureException
+ self.expected_regex = expected_regexp
def __enter__(self):
pass
@@ -268,10 +273,20 @@
exc_name = str(self.expected)
raise self.failureException(
"{0} not raised".format(exc_name))
- if issubclass(exc_type, self.expected):
+ if not issubclass(exc_type, self.expected):
+ # let unexpexted exceptions pass through
+ return False
+ if self.expected_regex is None:
return True
- # Let unexpected exceptions skip through
- return False
+
+ expected_regexp = self.expected_regex
+ if isinstance(expected_regexp, basestring):
+ expected_regexp = re.compile(expected_regexp)
+ if not expected_regexp.search(str(exc_value)):
+ raise self.failureException('"%s" does not match "%s"' %
+ (expected_regexp.pattern, str(exc_value)))
+ return True
+
class TestCase(object):
@@ -315,6 +330,31 @@
(self.__class__, methodName))
self._testMethodDoc = testMethod.__doc__
+ # Map types to custom assertEqual functions that will compare
+ # instances of said type in more detail to generate a more useful
+ # error message.
+ self.__type_equality_funcs = {}
+ self.addTypeEqualityFunc(dict, self.assertDictEqual)
+ self.addTypeEqualityFunc(list, self.assertListEqual)
+ self.addTypeEqualityFunc(tuple, self.assertTupleEqual)
+ self.addTypeEqualityFunc(set, self.assertSetEqual)
+ self.addTypeEqualityFunc(frozenset, self.assertSetEqual)
+
+ def addTypeEqualityFunc(self, typeobj, function):
+ """Add a type specific assertEqual style function to compare a type.
+
+ This method is for use by TestCase subclasses that need to register
+ their own type equality functions to provide nicer error messages.
+
+ Args:
+ typeobj: The data type to call this function on when both values
+ are of the same type in assertEqual().
+ function: The callable taking two arguments and an optional
+ msg= argument that raises self.failureException with a
+ useful error message when the two arguments are not equal.
+ """
+ self.__type_equality_funcs[typeobj] = function
+
def setUp(self):
"Hook method for setting up the test fixture before exercising it."
pass
@@ -330,14 +370,22 @@
return TestResult()
def shortDescription(self):
- """Returns a one-line description of the test, or None if no
- description has been provided.
+ """Returns both the test method name and first line of its docstring.
- The default implementation of this method returns the first line of
- the specified test method's docstring.
+ If no docstring is given, only returns the method name.
+
+ This method overrides unittest.TestCase.shortDescription(), which
+ only returns the first line of the docstring, obscuring the name
+ of the test upon failure.
"""
- doc = self._testMethodDoc
- return doc and doc.split("\n")[0].strip() or None
+ desc = str(self)
+ doc_first_line = None
+
+ if self._testMethodDoc:
+ doc_first_line = self._testMethodDoc.split("\n")[0].strip()
+ if doc_first_line:
+ desc = '\n'.join((desc, doc_first_line))
+ return desc
def id(self):
return "%s.%s" % (_strclass(self.__class__), self._testMethodName)
@@ -443,18 +491,45 @@
with self.failUnlessRaises(some_error_class):
do_something()
"""
- context = AssertRaisesContext(excClass, self)
+ context = _AssertRaisesContext(excClass, self)
if callableObj is None:
return context
with context:
callableObj(*args, **kwargs)
+ def _getAssertEqualityFunc(self, first, second):
+ """Get a detailed comparison function for the types of the two args.
+
+ Returns: A callable accepting (first, second, msg=None) that will
+ raise a failure exception if first != second with a useful human
+ readable error message for those types.
+ """
+ #
+ # NOTE(gregory.p.smith): I considered isinstance(first, type(second))
+ # and vice versa. I opted for the conservative approach in case
+ # subclasses are not intended to be compared in detail to their super
+ # class instances using a type equality func. This means testing
+ # subtypes won't automagically use the detailed comparison. Callers
+ # should use their type specific assertSpamEqual method to compare
+ # subclasses if the detailed comparison is desired and appropriate.
+ # See the discussion in http://bugs.python.org/issue2578.
+ #
+ if type(first) is type(second):
+ return self.__type_equality_funcs.get(type(first),
+ self._baseAssertEqual)
+ return self._baseAssertEqual
+
+ def _baseAssertEqual(self, first, second, msg=None):
+ """The default assertEqual implementation, not type specific."""
+ if not first == second:
+ raise self.failureException(msg or '%r != %r' % (first, second))
+
def failUnlessEqual(self, first, second, msg=None):
"""Fail if the two objects are unequal as determined by the '=='
operator.
"""
- if not first == second:
- raise self.failureException(msg or '%r != %r' % (first, second))
+ assertion_func = self._getAssertEqualityFunc(first, second)
+ assertion_func(first, second, msg=msg)
def failIfEqual(self, first, second, msg=None):
"""Fail if the two objects are equal as determined by the '=='
@@ -504,6 +579,356 @@
assertFalse = failIf
+ def assertSequenceEqual(self, seq1, seq2, msg=None, seq_type=None):
+ """An equality assertion for ordered sequences (like lists and tuples).
+
+ For the purposes of this function, a valid orderd sequence type is one
+ which can be indexed, has a length, and has an equality operator.
+
+ Args:
+ seq1: The first sequence to compare.
+ seq2: The second sequence to compare.
+ seq_type: The expected datatype of the sequences, or None if no
+ datatype should be enforced.
+ msg: Optional message to use on failure instead of a list of
+ differences.
+ """
+ if seq_type != None:
+ seq_type_name = seq_type.__name__
+ if not isinstance(seq1, seq_type):
+ raise self.failureException('First sequence is not a %s: %r'
+ % (seq_type_name, seq1))
+ if not isinstance(seq2, seq_type):
+ raise self.failureException('Second sequence is not a %s: %r'
+ % (seq_type_name, seq2))
+ else:
+ seq_type_name = "sequence"
+
+ differing = None
+ try:
+ len1 = len(seq1)
+ except (TypeError, NotImplementedError):
+ differing = 'First %s has no length. Non-sequence?' % (
+ seq_type_name)
+
+ if differing is None:
+ try:
+ len2 = len(seq2)
+ except (TypeError, NotImplementedError):
+ differing = 'Second %s has no length. Non-sequence?' % (
+ seq_type_name)
+
+ if differing is None:
+ if seq1 == seq2:
+ return
+
+ for i in xrange(min(len1, len2)):
+ try:
+ item1 = seq1[i]
+ except (TypeError, IndexError, NotImplementedError):
+ differing = ('Unable to index element %d of first %s\n' %
+ (i, seq_type_name))
+ break
+
+ try:
+ item2 = seq2[i]
+ except (TypeError, IndexError, NotImplementedError):
+ differing = ('Unable to index element %d of second %s\n' %
+ (i, seq_type_name))
+ break
+
+ if item1 != item2:
+ differing = ('First differing element %d:\n%s\n%s\n' %
+ (i, item1, item2))
+ break
+ else:
+ if (len1 == len2 and seq_type is None and
+ type(seq1) != type(seq2)):
+ # The sequences are the same, but have differing types.
+ return
+ # A catch-all message for handling arbitrary user-defined
+ # sequences.
+ differing = '%ss differ:\n' % seq_type_name.capitalize()
+ if len1 > len2:
+ differing = ('First %s contains %d additional '
+ 'elements.\n' % (seq_type_name, len1 - len2))
+ try:
+ differing += ('First extra element %d:\n%s\n' %
+ (len2, seq1[len2]))
+ except (TypeError, IndexError, NotImplementedError):
+ differing += ('Unable to index element %d '
+ 'of first %s\n' % (len2, seq_type_name))
+ elif len1 < len2:
+ differing = ('Second %s contains %d additional '
+ 'elements.\n' % (seq_type_name, len2 - len1))
+ try:
+ differing += ('First extra element %d:\n%s\n' %
+ (len1, seq2[len1]))
+ except (TypeError, IndexError, NotImplementedError):
+ differing += ('Unable to index element %d '
+ 'of second %s\n' % (len1, seq_type_name))
+ if not msg:
+ msg = '\n'.join(difflib.ndiff(pprint.pformat(seq1).splitlines(),
+ pprint.pformat(seq2).splitlines()))
+ self.fail(differing + msg)
+
+ def assertListEqual(self, list1, list2, msg=None):
+ """A list-specific equality assertion.
+
+ Args:
+ list1: The first list to compare.
+ list2: The second list to compare.
+ msg: Optional message to use on failure instead of a list of
+ differences.
+
+ """
+ self.assertSequenceEqual(list1, list2, msg, seq_type=list)
+
+ def assertTupleEqual(self, tuple1, tuple2, msg=None):
+ """A tuple-specific equality assertion.
+
+ Args:
+ tuple1: The first tuple to compare.
+ tuple2: The second tuple to compare.
+ msg: Optional message to use on failure instead of a list of
+ differences.
+ """
+ self.assertSequenceEqual(tuple1, tuple2, msg, seq_type=tuple)
+
+ def assertSetEqual(self, set1, set2, msg=None):
+ """A set-specific equality assertion.
+
+ Args:
+ set1: The first set to compare.
+ set2: The second set to compare.
+ msg: Optional message to use on failure instead of a list of
+ differences.
+
+ For more general containership equality, assertSameElements will work
+ with things other than sets. This uses ducktyping to support
+ different types of sets, and is optimized for sets specifically
+ (parameters must support a difference method).
+ """
+ try:
+ difference1 = set1.difference(set2)
+ except TypeError, e:
+ self.fail('invalid type when attempting set difference: %s' % e)
+ except AttributeError, e:
+ self.fail('first argument does not support set difference: %s' % e)
+
+ try:
+ difference2 = set2.difference(set1)
+ except TypeError, e:
+ self.fail('invalid type when attempting set difference: %s' % e)
+ except AttributeError, e:
+ self.fail('second argument does not support set difference: %s' % e)
+
+ if not (difference1 or difference2):
+ return
+
+ if msg is not None:
+ self.fail(msg)
+
+ lines = []
+ if difference1:
+ lines.append('Items in the first set but not the second:')
+ for item in difference1:
+ lines.append(repr(item))
+ if difference2:
+ lines.append('Items in the second set but not the first:')
+ for item in difference2:
+ lines.append(repr(item))
+ self.fail('\n'.join(lines))
+
+ def assertIn(self, a, b, msg=None):
+ """Just like self.assert_(a in b), but with a nicer default message."""
+ if msg is None:
+ msg = '"%s" not found in "%s"' % (a, b)
+ self.assert_(a in b, msg)
+
+ def assertNotIn(self, a, b, msg=None):
+ """Just like self.assert_(a not in b), but with a nicer default message."""
+ if msg is None:
+ msg = '"%s" unexpectedly found in "%s"' % (a, b)
+ self.assert_(a not in b, msg)
+
+ def assertDictEqual(self, d1, d2, msg=None):
+ self.assert_(isinstance(d1, dict), 'First argument is not a dictionary')
+ self.assert_(isinstance(d2, dict), 'Second argument is not a dictionary')
+
+ if d1 != d2:
+ self.fail(msg or ('\n' + '\n'.join(difflib.ndiff(
+ pprint.pformat(d1).splitlines(),
+ pprint.pformat(d2).splitlines()))))
+
+ def assertDictContainsSubset(self, expected, actual, msg=None):
+ """Checks whether actual is a superset of expected."""
+ missing = []
+ mismatched = []
+ for key, value in expected.iteritems():
+ if key not in actual:
+ missing.append(key)
+ elif value != actual[key]:
+ mismatched.append('%s, expected: %s, actual: %s' % (key, value,
+ actual[key]))
+
+ if not (missing or mismatched):
+ return
+
+ missing_msg = mismatched_msg = ''
+ if missing:
+ missing_msg = 'Missing: %s' % ','.join(missing)
+ if mismatched:
+ mismatched_msg = 'Mismatched values: %s' % ','.join(mismatched)
+
+ if msg:
+ msg = '%s: %s; %s' % (msg, missing_msg, mismatched_msg)
+ else:
+ msg = '%s; %s' % (missing_msg, mismatched_msg)
+ self.fail(msg)
+
+ def assertSameElements(self, expected_seq, actual_seq, msg=None):
+ """An unordered sequence specific comparison.
+
+ Raises with an error message listing which elements of expected_seq
+ are missing from actual_seq and vice versa if any.
+ """
+ try:
+ expected = set(expected_seq)
+ actual = set(actual_seq)
+ missing = list(expected.difference(actual))
+ unexpected = list(actual.difference(expected))
+ missing.sort()
+ unexpected.sort()
+ except TypeError:
+ # Fall back to slower list-compare if any of the objects are
+ # not hashable.
+ expected = list(expected_seq)
+ actual = list(actual_seq)
+ expected.sort()
+ actual.sort()
+ missing, unexpected = _SortedListDifference(expected, actual)
+ errors = []
+ if missing:
+ errors.append('Expected, but missing:\n %r\n' % missing)
+ if unexpected:
+ errors.append('Unexpected, but present:\n %r\n' % unexpected)
+ if errors:
+ self.fail(msg or ''.join(errors))
+
+ def assertMultiLineEqual(self, first, second, msg=None):
+ """Assert that two multi-line strings are equal."""
+ self.assert_(isinstance(first, types.StringTypes), (
+ 'First argument is not a string'))
+ self.assert_(isinstance(second, types.StringTypes), (
+ 'Second argument is not a string'))
+
+ if first != second:
+ raise self.failureException(
+ msg or '\n' + ''.join(difflib.ndiff(first.splitlines(True),
+ second.splitlines(True))))
+
+ def assertLess(self, a, b, msg=None):
+ """Just like self.assert_(a < b), but with a nicer default message."""
+ if msg is None:
+ msg = '"%r" unexpectedly not less than "%r"' % (a, b)
+ self.assert_(a < b, msg)
+
+ def assertLessEqual(self, a, b, msg=None):
+ """Just like self.assert_(a <= b), but with a nicer default message."""
+ if msg is None:
+ msg = '"%r" unexpectedly not less than or equal to "%r"' % (a, b)
+ self.assert_(a <= b, msg)
+
+ def assertGreater(self, a, b, msg=None):
+ """Just like self.assert_(a > b), but with a nicer default message."""
+ if msg is None:
+ msg = '"%r" unexpectedly not greater than "%r"' % (a, b)
+ self.assert_(a > b, msg)
+
+ def assertGreaterEqual(self, a, b, msg=None):
+ """Just like self.assert_(a >= b), but with a nicer default message."""
+ if msg is None:
+ msg = '"%r" unexpectedly not greater than or equal to "%r"' % (a, b)
+ self.assert_(a >= b, msg)
+
+ def assertIsNone(self, obj, msg=None):
+ """Same as self.assert_(obj is None), with a nicer default message."""
+ if msg is None:
+ msg = '"%s" unexpectedly not None' % obj
+ self.assert_(obj is None, msg)
+
+ def assertIsNotNone(self, obj, msg='unexpectedly None'):
+ """Included for symmetry with assertIsNone."""
+ self.assert_(obj is not None, msg)
+
+ def assertRaisesRegexp(self, expected_exception, expected_regexp,
+ callable_obj=None, *args, **kwargs):
+ """Asserts that the message in a raised exception matches a regexp.
+
+ Args:
+ expected_exception: Exception class expected to be raised.
+ expected_regexp: Regexp (re pattern object or string) expected
+ to be found in error message.
+ callable_obj: Function to be called.
+ args: Extra args.
+ kwargs: Extra kwargs.
+ """
+ context = _AssertRaisesContext(expected_exception, self, expected_regexp)
+ if callable_obj is None:
+ return context
+ with context:
+ callable_obj(*args, **kwargs)
+
+ def assertRegexpMatches(self, text, expected_regex, msg=None):
+ if isinstance(expected_regex, basestring):
+ expected_regex = re.compile(expected_regex)
+ if not expected_regex.search(text):
+ msg = msg or "Regexp didn't match"
+ msg = '%s: %r not found in %r' % (msg, expected_regex.pattern, text)
+ raise self.failureException(msg)
+
+
+def _SortedListDifference(expected, actual):
+ """Finds elements in only one or the other of two, sorted input lists.
+
+ Returns a two-element tuple of lists. The first list contains those
+ elements in the "expected" list but not in the "actual" list, and the
+ second contains those elements in the "actual" list but not in the
+ "expected" list. Duplicate elements in either input list are ignored.
+ """
+ i = j = 0
+ missing = []
+ unexpected = []
+ while True:
+ try:
+ e = expected[i]
+ a = actual[j]
+ if e < a:
+ missing.append(e)
+ i += 1
+ while expected[i] == e:
+ i += 1
+ elif e > a:
+ unexpected.append(a)
+ j += 1
+ while actual[j] == a:
+ j += 1
+ else:
+ i += 1
+ try:
+ while expected[i] == e:
+ i += 1
+ finally:
+ j += 1
+ while actual[j] == a:
+ j += 1
+ except IndexError:
+ missing.extend(expected[i:])
+ unexpected.extend(actual[j:])
+ break
+ return missing, unexpected
+
class TestSuite(object):
"""A test suite is a composite test consisting of a number of TestCases.