Testing

Testing in Python

Testing ensures that our code works as expected and helps catch errors early.

Test file is used before releasing the main file to the world

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Code Quality Tools

• pylint → checks code for errors and enforces coding standards.
• pyflakes → detects errors without enforcing style.
• autopep8 → automatically formats code according to PEP8 guidelines.

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Unit Testing with unittest

Python has a built-in module called unittest for writing and running tests.

Basic Setup

import unittest

class TestExercise(unittest.TestCase):
    def test_input(self):
        pass

if __name__ == '__main__':
    unittest.main()

Testing a Function

Example: Testing a Guessing Function

main file

import random

print('GUESS A NUMBER')

def run_guess(guess, answer):
    if 0 < guess < 11:
            if guess is answer:
                print('You are a genius')
                return True
    else:
        print('try again')
        return False

if __name__ == '__main__':
    answer = random.randint(1, 10)
    print(answer)
    while True:
        try:
            guess = int(input('guess a numbers 1-10: '))
            if run_guess(guess, answer):
                break
        except ValueError:
            print('you did something wrong')
            continue

test file

import unittest
import Exercise

class TestExercise(unittest.TestCase):
    def test_input(self):
        result = Exercise.run_guess(5, 5)
        self.assertTrue(result)
    # this test case when the guess is correct, which is 5, and the expected result is True

    def test_input2(self):
        result = Exercise.run_guess(0, 5)
        self.assertFalse(result)
    # this test case is testing the case when the guess is 0, which is not a valid guess, and the expected result is False

    def test_input3(self):
        result = Exercise.run_guess(11, 5)
        self.assertFalse(result)

    def test_input4(self):
        result = Exercise.run_guess(5, '5')
        self.assertFalse(result)

if __name__ == '__main__':
    unittest.main(verbosity=2)

Example: Testing a Function

main file

def do_stuff(num=0):
    try:
        if num:
            return int(num) + 5
        else:
            raise ValueError("No parameter provided")
    except ValueError as err:
        return err

test file

import unittest
import main

class TestMain(unittest.TestCase):
    def setUp(self):
        print('About to run a function')

    def test_do_stuff(self):
        '''Hiii'''
        test_parameter = 1
        result = main.do_stuff(test_parameter)
        self.assertEqual(result, 6)

    def test_do_stuff2(self):
        test_parameter = 'woahh'
        result = main.do_stuff(test_parameter)
        self.assertIsInstance(result, ValueError)

    def test_do_stuff3(self):
        test_parameter = None
        result = main.do_stuff(test_parameter)
        self.assertEqual(str(result), 'No parameter provided')

    def tearDown(self):
        print('Cleaning up...')     #setup and teardown are used to run code before and after each test case.


if __name__ == '__main__':
    unittest.main(verbosity=2)

• setUp() → runs before each test case.

• tearDown() → runs after each test case.

• verbosity=2 → shows detailed test results.

Run tests with:

python -m unittest test_main.py

Understanding Unit Test Details

• The verbosity=2 argument in unittest.main() is used to display the name of each test and its result (ok or fail).
• Test cases are defined inside the TestMain class, and each test case must be written as a method that starts with the word test.
• You can add comments or docstrings to test methods to explain:
• What the test case is checking.
• What the expected result should be.

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Why Testing Matters

• Tests are used to check our code as thoroughly as possible.
• Even with a simple function, writing multiple test cases helps uncover small issues that might otherwise go unnoticed.
• Tests catch small issues early and improve code reliability and quality of our code.