Issue #4444: Allow assertRaises() to be used as a context handler.
diff --git a/Lib/unittest.py b/Lib/unittest.py
index 09c6ca9..4538e30 100644
--- a/Lib/unittest.py
+++ b/Lib/unittest.py
@@ -174,6 +174,25 @@
(_strclass(self.__class__), self.testsRun, len(self.errors),
len(self.failures))
+class AssertRaisesContext:
+ def __init__(self, expected, test_case):
+ self.expected = expected
+ self.failureException = test_case.failureException
+ def __enter__(self):
+ pass
+ def __exit__(self, exc_type, exc_value, traceback):
+ if exc_type is None:
+ try:
+ exc_name = self.expected.__name__
+ except AttributeError:
+ exc_name = str(self.expected)
+ raise self.failureException(
+ "{0} not raised".format(exc_name))
+ if issubclass(exc_type, self.expected):
+ return True
+ # Let unexpected exceptions skip through
+ return False
+
class TestCase:
"""A class whose instances are single test cases.
@@ -324,22 +343,25 @@
"""Fail the test unless the expression is true."""
if not expr: raise self.failureException, msg
- def failUnlessRaises(self, excClass, callableObj, *args, **kwargs):
+ def failUnlessRaises(self, excClass, callableObj=None, *args, **kwargs):
"""Fail unless an exception of class excClass is thrown
by callableObj when invoked with arguments args and keyword
arguments kwargs. If a different type of exception is
thrown, it will not be caught, and the test case will be
deemed to have suffered an error, exactly as for an
unexpected exception.
+
+ If called with callableObj omitted or None, will return a
+ context object used like this::
+
+ with self.failUnlessRaises(some_error_class):
+ do_something()
"""
- try:
+ context = AssertRaisesContext(excClass, self)
+ if callableObj is None:
+ return context
+ with context:
callableObj(*args, **kwargs)
- except excClass:
- return
- else:
- if hasattr(excClass,'__name__'): excName = excClass.__name__
- else: excName = str(excClass)
- raise self.failureException, "%s not raised" % excName
def failUnlessEqual(self, first, second, msg=None):
"""Fail if the two objects are unequal as determined by the '=='