unittests for infinite loop

Question

I am stucked at this code for creating unittest for infinite loop.

try:
  while True:
    time.sleep(60)
except:
  fun()

Please let me know how can we create unittests for infinite loop?

Answer 1

What behaviour are you testing? There doesn't appear to be any side effects or return value here. There isn't really anything to test. If it's just that fun is called after the loop then that sounds like over-specification. If it's just that some invariant is maintained after the loop ends then you can patch sleep to throw an exception, and then examine the state after the function has run.

from unittest import TestCase, main
from unittest.mock import patch

import module_under_test

class TestLoop(TestCase):
    # patch sleep to allow loop to exit
    @patch("time.sleep", side_effect=InterruptedError)
    def test_state_reset(self, mocked_sleep):
        # given
        obj = module_under_test.SomeClass()

        # when
        obj.infinite_loop()

        # then assert that state is maintained
        self.assertFalse(obj.running)

if __name__ == "__main__":
    main()

module_under_test.py

import time

class SomeClass:
    def __init__(self):
        self.running = False

    def fun(self):
        self.running = False

    def infinite_loop(self):
        self.running = True
        try:
            while True:
                time.sleep(60)
        except:
            self.fun()