Unit Test

Debugging 偵錯

assert

可用在程式的條件測試 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

Linux strace Command Tutorial for Beginners (8 Examples)

# 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

pdb

功能：

設定程式中斷點 逐行檢查程式碼 檢查變數 以互動方式評估表達式

pdb3 myprog.py

pdb-subcommands

continue : 繼續執行直到異常的程式碼 print() : 輸出變數的內容

(Pdb) continue
...
(Pdb) print(row)

Step 1: Set a breakpoint

import pdb


def add_numbers(a, b):
    pdb.set_trace()  # This will set a breakpoint in the code
    result = a + b
    return result


print(add_numbers(3, 4))

Setp 2: Enter the interactive debugger

a (args): Show the arguments of the current function.

b: Manually set a persistent breakpoint while in debugger.

n (next): Execute the next line within the current function.

s (step): Execute the current line and stop at the first possible occasion (e.g., in a function that is called).

c (continue): Resume normal execution until the next breakpoint.

p (print): Evaluate and print the expression, e.g., p variable_name will print the value of variable_name.

Pp (pretty-print): Pretty-print the value of the expression.

q (quit): Exit the debugger and terminate the program.

r (return): Continue execution until the current function returns.

tbreak: Manually set a temporary breakpoint that goes away once hit the first time.

!: Prefix to execute an arbitrary Python command in the current environment, e.g., !variable_name = "new_value" will set variable_name to "new_value".

Step 3: Inspect variables

To inspect the variables, simply type the single character, p, then the variable name to see its current value. For instance, if you have a variable in your code named sentiment_score, just type p sentiment_score at the pdb prompt to inspect its value.

Step 4: Modify variables

A big advantage of pdb is that you can change the value of a variable directly in the debugger. For example, to change sentiment_score to 0.9, you'd type !sentiment_score = 0.9.

To confirm these changes, use a or directly probe the value with p <value name>.

 Step 5: Exit the debugger

When you’re done, simply enter q (quit) to exit the debugger and terminate the program.

Post-mortem debugging

python -m pdb your_script.py

 

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

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

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