python testing code coverage and multiple asserts in one test function

Question

In the following code,

1.If we assert the end result of a function then is it right to say that we have covered all lines of the code while testing or we have to test each line of the code explicitly if so how ?

2.Also Is it fine that we can have the positive ,negative and more assert statements in one single test function.If not please give examples

def get_wcp(book_id):
    update_tracking_details(book_id)
    c_id = get_new_supreme(book_id)
    if book_id == c_id:
       return True
    return False

class BookingentitntyTest(TestCase):
    def setUp(self):
       self.booking_id = 123456789# 9 digit number poistive test case

    def test_get_wcp(self):
       retVal = get_wcp(self.book_id)
       self.assertTrue( retVal )
       self.booking_id = 1# 1 digit number Negative test case
       retVal = get_wcp(self.book_id)
       self.assertFalse( retVal )

Answer 1

1. No, just because you asserted the final result of the statement doesn't mean all paths of your code has been evaluated. You don't need to write "test each line" in the sense that you only need to go through all the code paths possible.

2. As a general guideline, try to keep the number of assert statements in a test as minimum as possible. When one assert statement fails, the further statements are not executed, and doesn't count as failures which is often not required.

Besides try to write your tests as elegantly as possible, even more so than the code they are testing. We wouldn't want to write tests to test our tests, now would we?

  def test_get_wcp_returns_true_when_valid_booking_id(self):
      self.assertTrue(get_wcp(self.book_id))

  def test_get_wcp_returns_false_if_invalid_booking_id(self):
      self.assertFalse(get_wcp(1))

Complete bug-free code is not possible.

"Testing shows the presence, not the absence of bugs" - Edsger Dijkstra.