A quick fiddle with which you can assert that httmock was called in a certain way.

httmock_assert.py

class httmock_assert:
    def __init__(self, method=None, url=None):
        self.method = method
        self.url = url
        self.data = None
        self.headers = []
        self.response = {'status_code': 200}

    def assert_header(self, key, value):
        self.headers.append((key, value))
        return self

    def assert_data(self, data):
        self.data = data
        return self


    def and_return_on_success(self, httmock_dict):
        self.response = httmock_dict
        return self

    def __call__(self, *args, **kwargs):
        url, request = args

        if self.method:
            assert_that(request.method, is_(self.method))

        if self.url:
            assert_that(request.url, is_(self.url))

        if self.data:
            assert_that(request.data, is_(self.data))

        for k, v in self.headers:
            assert_that(request.headers, has_entry(k, v))

        # If we came this far no assert failed. Hooray!
        return self.response