How To Unit Test Time Based Functions Without Adding Parameters

I created a function that returns seconds left until the next occurrence of that time, but I came across a problem writing a unit test for it. How do people test this type of funct

Solution 1:

You need to use mocking framework to isolate your UT from dependencies so your UT will have a consistence behavior.

Freezegun - is a good mocking library for times which I have been used.

Just install this library: pip install freezegun

The in your UT used the decorator @freeze_time as the following:

@freeze_time("2018-06-03") deftest_time_left(self):
    dt_now = datetime.now()
    tm_5sec_future = (dt_now + timedelta(0, 5)).time()
    self.assertEqual(dtime.get_time_left(tm_5sec_future), -5.0)