Here's another example of the point I was trying to make. If this assertion fails, is it because `job.cancel()` failed or is it because `self.client.jobs[]` failed?  It's hard to know without thinking about it. Making it a separate test (which in the case of `test_data_access` is already the case) makes it clearer. It would be even more clear if the cancellation occurred in a test of its own rather than mixed into the `test_put_get`.