Looks pretty good to me, but you may want to doublecheck some of your test criteria.

Firstly, the two "*_with_exception" checks don't look quite right to me. I would have expected to see something like the following for both of them: 

  self.assertIsNotNone(context.exc)
  self.assertIs(context.exc[0], NameError).

Secondly, I can't even begin to guess what the method decoration test is currently trying to show. Why 3 instantiations? Why check the instance assignments rather than the context manager behaviour? Either I'm completely missing something, or this currently isn't testing what you meant to test :)

Finally, you may as well include a second typo test to cover the __enter__ misspelling case.