Testing Django Signals Emission

assertion.py

from collections import Mapping
from dataclasses import dataclass
from typing import Any, Tuple


@dataclass()
class SignalHandlerContext:
    sender: Any
    args: Tuple[Any]
    kwargs: Mapping


class InterceptSignal:
    def __init__(self, signal):
        self._signal = signal
        self._call_args = []

    def __enter__(self):
        self._signal.connect(self._signal_handler)
        return self

    def __exit__(self, exc_type, exc_val, exc_tb):
        self._signal.disconnect(self._signal_handler)

    def _signal_handler(self, sender, *args, **kwargs):
        self._call_args.append(SignalHandlerContext(sender=sender, args=args, kwargs=kwargs))

    @property
    def call_args(self):
        return self._call_args

    @property
    def call_count(self):
        return len(self._call_args)

tests.py

from django.test import TestCase

class SomeTestCase(TestCase):
  def test_something(self):
    with InterceptSignal(signal=my_custom_signal) as signal_data:
        # Invoke functions that will emit the signal specified
        self.assertEqual(signal_data.call_count, 1)