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
  

test_example.py

import pytest

def test_addition():
    assert 1 + 1 == 3


class TestMathOperations:
    def test_addition(self):
        assert 1 + 1 == 2

Functio-based: pytest test_example.py::test_addition 

Class-based:

• pytest test_example.py::TestMathOperations 
• pytest test_example.py::TestMathOperations::test_addition 

pytest Raises

程式碼異常/錯誤訊息的測試

Checking for ValueError (不正確數值)

import pytest
 import math

 def calculate_square_root(value):
     if value < 0:
         raise ValueError("Cannot calculate the square root of a negative number")
     return math.sqrt(value)

 def test_calculate_square_root():
     with pytest.raises(ValueError):
         calculate_square_root(-1)

Checking for ZeroDivisionError (零除誤差)

 import pytest

 def divide_numbers(numerator, denominator):
     return numerator / denominator

 def test_divide_numbers():
     with pytest.raises(ZeroDivisionError):
         divide_numbers(10, 0)

Checking for TypeError (資料類型錯誤)

import pytest

 def add_numbers(a, b):
     return a + b

 def test_add_numbers():
     with pytest.raises(TypeError):
         add_numbers("10", 5)

Checking for KeyError (字典的鍵值錯誤)

 import pytest

 def get_value(dictionary, key):
     return dictionary[key]

 def test_get_value():
     with pytest.raises(KeyError):
         get_value({"name": "Alice"}, "age")

pytest Markers

無條件忽略

@pytest.mark.skip(reason="Feature not yet implemented")
 def test_feature():
     pass

有條件忽略

import sys

 @pytest.mark.skipif(sys.platform == "win32", reason="does not run on windows")
 class TestClass:
     def test_function(self):
         "This test will not run under 'win32' platform"

pytest Fixtures

可重複使用的預設資料

import pytest

@pytest.fixture
def user_data():
    return [
        {"name": "Alice", "age": 30},
        {"name": "Bob", "age": 25},
        {"name": "Charlie", "age": 35}
    ]

# Test function to check for a specific user by name and age
def test_user_exists(user_data):
    user = {"name": "Alice", "age": 30}

    # Check if the target user is in the list
    assert user in user_data

# Test average age of users
def test_average_age(user_data):
    ages = [user["age"] for user in user_data]
    avg_age = sum(ages) / len(ages)
    assert avg_age == 30

pytest Parametrization

可同時使用不同資料集執行測試函式。

import pytest

# Function to calculate the square of a number
def square_numbers(num):
    return num * num

#Parametrize decorator to test the square function with different inputs
@pytest.mark.parametrize("input_value, expected_output", [
    (2, 4),     
    (-3, 9),    
    (0, 0)    
])

def test_square(input_value, expected_output):
    assert square_numbers(input_value) == expected_output

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