Helper decorator for Django unittests, used to make sure that the expected signals were fired the expected number of times.

gistfile1.py

"""
Helper decorator for Django unittests, used to make sure that the expected 
signals were fired the expected number of times.
Usage:

    class MyTestCase(TestCase):

        @assert_signal_fired({
            'my_signal_func': (my_signal_func, 1),
            'other_signal_func': (other_signal_func, 0)
        })
        def test_something(self):
            ...test code here

It will connect a temporary handler function to the specified signals, count 
the number of times those signals were invoked and at the end of the test 
assert whether the signals were called the expected number of times, and will
properly clean up after itself by disconnecting the temporary signal handlers.
"""
from functools import partial


def assert_signal_fired(expectations):
    _counters = {}

    def signal_fired_handler(signal_name, *args, **kwargs):
        _counters[signal_name] = _counters.get(signal_name, 0) + 1

    def _assert_signal_fired(func):
        def __assert_signal_fired(self, *args, **kwargs):
            _connected = []

            for signal_name, (signal_func, call_count) in expectations.items():
                handler = partial(signal_fired_handler, signal_name)
                signal_func.connect(handler)
                _connected.append((signal_name,
                                   signal_func,
                                   call_count,
                                   handler))

            result = func(self, *args, **kwargs)

            for conn in _connected:
                (signal_name, signal_func, expected_call_count, handler) = conn
                signal_func.disconnect(handler)
                call_count = _counters.get(signal_name, 0)
                msg = ('{0} was expected to be called {1} time(s), '
                       'but was called {2} time(s).')
                msg = msg.format(signal_name, expected_call_count, call_count)
                self.assertEqual(call_count, expected_call_count, msg=msg)

            return result
        return __assert_signal_fired
    return _assert_signal_fired