Ok, I figured this out, `mock.Mock(CQLClient)` only applies to that mock object _not_ the mock object acquired by getting `self.client.execute`.  You actually want to do
```
self.client = mock.create_autospec(CQLClient)
```

From: http://mock.readthedocs.org/en/latest/helpers.html#autospeccing

Autospeccing is based on the existing spec feature of mock. It limits the api of mocks to the api of an original object (the spec), but **it is recursive (implemented lazily) so that attributes of mocks only have the same api as the attributes of the spec.** In addition mocked functions / methods have the same call signature as the original so they raise a TypeError if they are called incorrectly.