Skip to main content

Debug & Test

Debugging 偵錯

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"

assert type(username) == str, "username must be a string"
prinf debugging
print("Processing {}".format(basename))
strace
# Installation on RHEL if it's not installed
yum install strace

# Tracing system calls made by a program
strace ./my-program.py
strace -o my-program.strace ./my-program
pdb3
pdb3 myprog.py

pdb-subcommands

  • continue : 繼續執行直到異常的程式碼
(Pdb) continue
...

 

 


Unit Test 單元測試

  • 目的：以隔離主程式的方式，對自訂的函式(function)與方法(method)，提供指定的輸入參數與期待的輸出結果，以驗證相關程式碼是否有瑕疵或錯誤。
  • 方法：撰寫額外的測試用程式碼，並使用任一個單元測試模組，例如 unittest, Pytest 或類似用途的其他模組。 
  • 自動化：整合 CI/CD 做到全自動化程式碼單元測試
Pytest
unittest

Methods

  • .assertEqual(a, b) : checks that a == b
  • .assertNotEqual(a, b) : checks that a != b
  • .assertTrue('FOO'.isupper()) : checks that bool(x) is True
  • .assertFalse('Foo'.isupper()) : checks that bool(x) is False 

Example 1: rearrange.py

#!/usr/bin/env python3

import re

def rearrange_name(name):
  result = re.search(r"^([\w .]*), ([\w .]*)$", name)
  if result is None:
    return name
  return "{} {}".format(result[2], result[1])

rearrange_test.py : 

#!/usr/bin/env python3

import unittest

from rearrange import rearrange_name

class TestRearrange(unittest.TestCase):
    
  def test_basic(self):  # Basic test case
    testcase = "Lovelace, Ada"
    expected = "Ada Lovelace"
    self.assertEqual(rearrange_name(testcase), expected)

  def test_empty(self):  # Edge case, such as zero, blank, negative numbers, or extremely large numbers
    testcase = ""
    expected = ""
    self.assertEqual(rearrange_name(testcase), expected)

  def test_double_name(self):   # Additional test case
    testcase = "Hopper, Grace M."
    expected = "Grace M. Hopper"
    self.assertEqual(rearrange_name(testcase), expected)

  def test_one_name(self):      # Additional test case
    testcase = "Voltaire"
    expected = "Voltaire"
    self.assertEqual(rearrange_name(testcase), expected)

# Run the tests
unittest.main()

Tip: 在 Jupyter 環境執行 unittest.main() 時可能會出現錯誤，修正方法是改成unittest.main(argv = ['first-arg-is-ignored'], exit = False))。

The output of the result:

.
----------------------------------------------------------------------
Ran 4 test in 0.000s

OK

Example 2: cakefactory.py

#!/usr/bin/env python3

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

cakefactory_test.py

#!/usr/bin/env python3

import unittest
from cakefactory import CakeFactory

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 4 test in 0.002s

OK

Back to top