django: test case for @property function of a Model

Question

I have a Django Library application which has the following BookInstance Model:

class BookInstance(models.Model):
    id = models.UUIDField(primary_key=True, default=uuid.uuid4,help_text='Unique ID for this particular book across whole library')
    book = models.ForeignKey('Book', on_delete=models.SET_NULL, null=True)
    due_back = models.DateField(null=True, blank=True)
    borrower = models.ForeignKey(User, on_delete=models.SET_NULL, null=True, blank=True)

    STATUS_MAINTENANCE = 'm'
    STATUS_ON_LOAN = 'o'
    STATUS_AVAILABLE = 'a'
    STATUS_RESERVED = 'r'

    LOAN_STATUS = (
      (STATUS_MAINTENANCE, 'Maintenance'),
      (STATUS_ON_LOAN, 'On loan'),
      (STATUS_AVAILABLE, 'Available'),
      (STATUS_RESERVED, 'Reserved'),
    )

    status = models.CharField(
       max_length=1,
       choices=LOAN_STATUS,
       blank=True,
       default=STATUS_MAINTENANCE,
       help_text='Book availability',
     )

    class Meta:
        ordering = ['due_back']
        permissions = (("can_mark_returned", "Set book as returned"), ("can_create_book", "Create new book"), ("can_update_book", "Update book details"), ("can_delete_book", "Delete book"),)


    # how to develop test case for this function
    @property
    def is_overdue(self):
       if self.due_back and date.today() > self.due_back:
        return True
    return False

In my tests.py file, I have the test_object_name_is_name function to test it, however my coverage report shows that the function is not getting tested.

class BookInstanceModelTest(TestCase):
"""
    Test case for Book Instance
"""
   @classmethod
   def setUpTestData(cls):
       # Set up non-modified objects used by all test methods
       test_user1 = User.objects.create_user(username='testuser1', password='1X<ISRUkw+tuK',
                                          email='testuser1@test.com')
       test_user2 = User.objects.create_user(username='testuser2', password='2HJ1vRV0Z&3iD',
                                          email='testuser2@test.com')

       test_author = Author.objects.create(first_name='William', last_name='Shakespeare')
       test_book = Book.objects.create(title='Hamlet', author=test_author, summary='Published in 1990',
                                    isbn='123456789123')
       genre_objects_for_book = Genre.objects.all()
       test_book.genre.set(genre_objects_for_book)

       return_date1 = datetime.date.today()
       BookInstance.objects.create(book=test_book, borrower=test_user1, due_back=return_date1,
                                status='o')
       return_date2 = datetime.date.today() + datetime.timedelta(days=5)
       BookInstance.objects.create(book=test_book, borrower=test_user2, due_back=return_date2,
                                status='o')

       return_date3 = datetime.date.today() - datetime.timedelta(days=5)
       BookInstance.objects.create(book=test_book, borrower=test_user2, due_back=return_date3,
                                status='o')

   # test case I developed
   def test_book_is_overdue(self):
       last_date = datetime.date.today()
       for book in BookInstance.objects.all():
          if book.due_back == last_date:
              self.assertTrue(True)
          elif book.due_back > last_date:
              self.assertTrue(True)
          elif book.due_back < last_date:
              self.assertFalse(False)

I have made a check whether the due_back is late or below the deadline, the Test executes successfully, and yet does not actually test the is_overdue() of BookInstance model. Please guide me how should I test this function correctly! Thanks

Answer 1

I think you misunderstood how test case works in django; you should prefix your test methods with test_ and then whatever name you want, but its not important for functionality nor it will call functions.

To test your property, you should call it in your test:

 def test_book_is_overdue(self):
       last_date = datetime.date.today()
       for book in BookInstance.objects.all():
          value = book.is_overdue
          # test whatever you want