I'm adding some assert tests to test_grammar.py to verify that the assert statement raises (or doesn't raise) an AssertionError properly.

NOTE: I'm currently helping Dino port IronPython tests into CPython. This is part of that series.

I propose you move all the assert test cases into there own test method and decorate it with @unittest.skipUnless(__debug__).

Wouldn't it be better to test e.args instead or in addition to str(e)?
Skipping the whole test if __debug__ is False is also a good idea.

I've uploaded new versions of the patch.

__debug__: I removed the "if __debug__" clause and switched to skipUnless.

Exception args: I replaced str(e) with e.args. Thanks for pointing that out! I had thought args was going to be deprecated but I guess it's not (Issue6777).

New changeset bcfb499338c1 by Ezio Melotti in branch '2.7':
#8414: add more tests for "assert".  Initial patch by Gregory Nofi.
http://hg.python.org/cpython/rev/bcfb499338c1

New changeset 1efefeda00a7 by Ezio Melotti in branch '3.2':
#8414: add more tests for "assert".  Initial patch by Gregory Nofi.
http://hg.python.org/cpython/rev/1efefeda00a7

New changeset 47afbb2033aa by Ezio Melotti in branch 'default':
#8414: merge with 3.2.
http://hg.python.org/cpython/rev/47afbb2033aa

Committed, thanks for the patch!
I preferred to add a separate test, because only the tests with "assert False" need to be skipped with -O, the other can run with and without -O.