[TIP] [ANN] CaptureMock 0.1 - honestly not just yet another mocking framework!

Geoff Bache geoff.bache at gmail.com
Thu Mar 24 14:14:37 PDT 2011

Hi all,

I can hear the groans already that here comes Python Mocking Framework
Number 15 with new and improved syntax on the other 14, but plase hear
me out for a paragraph or two! I've been following the Python mocking
framework discussions with interest and wondered about joining in with
my own contribution, but as this one is a bit different and is trying
to solve a slightly different problem I've stayed out of it so far.

The problem I'm (primarily) addressing is mocking out substantial
subsystems and third-party modules when doing functional tests, and
being easily able to handle the situation when the mocked subsystem
changes its behaviour. I've found in the past that it's easy for mocks
to diverge from what the real system does, and continue to pass even
when the real code will break. Where other mocking frameworks
primarily focus on mocking code that you own and write yourself,
CaptureMock is more about mocking out code that you don't own.

Anyway, I've created a mock framework that captures interaction with
any given module, attribute or function, and stores the results in a
text file. Any tests using it can then either be run in record or
replay mode each time they are run. An obvious setup is therefore to
ordinarily use replay mode but to re-record if anything in the
interaction changes. And perhaps to have a CI setup somewhere that
always uses record mode and hence verifies that the integration still

Using it doesn't really involve writing mock code like existing mock
tools do. It just requires saying what you want to capture:

from capturemock import capturemock

def test_something_sending_email():
     # etc

def test_some_real_time_code():
     # etc

def test_my_graph_stuff():
     # etc

For more details (including what the recorded format looks like), see
and obviously install from PyPI with "pip install capturemock" or similar.

Any feedback much appreciated. I've been using it for some time, it's
been hardwired into my TextTest tool until now, but it should be
regarded as Alpha outside that context for obvious reasons...

Geoff Bache

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