Debug & Test

Unit Test

Pytest

YT: How To Write Unit Tests in Python • Pytest Tutorial - YouTube

Debugging

assert

• assert <condition>, <message> : 如果 condition 為 True，沒有作用；如果為 False，會產生錯誤，並顯示訊息

x = 5
assert x == 5, "x should be 5"

Unit Test

Pytest

YT: How To Write Unit Tests in Python • Pytest Tutorial - YouTube

unittest

CakeFactory

from typing import List

class CakeFactory:
 def __init__(self, cake_type: str, size: str):
   self.cake_type = cake_type
   self.size = size
   self.toppings = []

   # Price based on cake type and size
   self.price = 10 if self.cake_type == "chocolate" else 8
   self.price += 2 if self.size == "medium" else 4 if self.size == "large" else 0

 def add_topping(self, topping: str):
     self.toppings.append(topping)
     # Adding 1 to the price for each topping
     self.price += 1

 def check_ingredients(self) -> List[str]:
     ingredients = ['flour', 'sugar', 'eggs']
     ingredients.append('cocoa') if self.cake_type == "chocolate" else ingredients.append('vanilla extract')
     ingredients += self.toppings
     return ingredients

 def check_price(self) -> float:
     return self.price

# Example of creating a cake and adding toppings
cake = CakeFactory("chocolate", "medium")
cake.add_topping("sprinkles")
cake.add_topping("cherries")
cake_ingredients = cake.check_ingredients()
cake_price = cake.check_price()


cake_ingredients, cake_price

TestCakeFactory

import unittest

class TestCakeFactory(unittest.TestCase):
 def test_create_cake(self):
   cake = CakeFactory("vanilla", "small")
   self.assertEqual(cake.cake_type, "vanilla")
   self.assertEqual(cake.size, "small")
   self.assertEqual(cake.price, 8) # Vanilla cake, small size

 def test_add_topping(self):
     cake = CakeFactory("chocolate", "large")
     cake.add_topping("sprinkles")
     self.assertIn("sprinkles", cake.toppings)

 def test_check_ingredients(self):
     cake = CakeFactory("chocolate", "medium")
     cake.add_topping("cherries")
     ingredients = cake.check_ingredients()
     self.assertIn("cocoa", ingredients)
     self.assertIn("cherries", ingredients)
     self.assertNotIn("vanilla extract", ingredients)

 def test_check_price(self):
     cake = CakeFactory("vanilla", "large")
     cake.add_topping("sprinkles")
     cake.add_topping("cherries")
     price = cake.check_price()
     self.assertEqual(price, 13) # Vanilla cake, large size + 2 toppings


# Running the unittests
unittest.TextTestRunner().run(unittest.TestLoader().loadTestsFromTestCase(TestCakeFactory))

This results in the output:

..F.
======================================================================
FAIL: test_check_price (__main__.TestCakeFactory)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "<ipython-input-9-32dbf74b3655>", line 33, in test_check_price
    self.assertEqual(price, 13) # Vanilla cake, large size + 2 toppings
AssertionError: 14 != 13

----------------------------------------------------------------------
Ran 4 tests in 0.007s

FAILED (failures=1)
<unittest.runner.TextTestResult run=4 errors=0 failures=1>

The program calls the TextTestRunner() method, which returns a runner (TextTestResult). It says one failure occurred: the statement self.assertEqual(price, 13) was incorrect, as it should have been 14. How can we correct that part of the test? Update that part of the code to the following:

import unittest


# Fixing the test_check_price method
class TestCakeFactory(unittest.TestCase):
 # ... Other tests remain the same

 def test_check_price(self):
     cake = CakeFactory("vanilla", "large")
     cake.add_topping("sprinkles")
     cake.add_topping("cherries")
     price = cake.check_price()
     self.assertEqual(price, 14) # Vanilla cake, large size + 2 toppings

# Re-running the unittests
unittest.TextTestRunner().run(unittest.TestLoader().loadTestsFromTestCase(TestCakeFactory))

And now the program works as expected, as the results provide no failures and are:

.
----------------------------------------------------------------------
Ran 1 test in 0.002s

OK
<unittest.runner.TextTestResult run=1 errors=0 failures=0>