python unit testing ( AI generated)

To test Python code unit by unit, you use unit testing frameworks like unittest (built-in), pytest, or nose2. Here's a step-by-step guide:

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1. Write Testable Code

Ensure your code is modular, with each function or method performing a specific task.

Example Python Code (math_operations.py):

def add(a, b):

    return a + b

def divide(a, b):

    if b == 0:

        raise ValueError("Cannot divide by zero")

    return a / b

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2. Use a Unit Testing Framework

Using unittest (Built-in Framework)

1. Create a test file (e.g., test_math_operations.py).

2. Import the unittest module and the functions to be tested.

3. Define test cases by subclassing unittest.TestCase.

Example:

import unittest

from math_operations import add, divide

class TestMathOperations(unittest.TestCase):

    def test_add(self):

        self.assertEqual(add(2, 3), 5)

        self.assertEqual(add(-1, 1), 0)

    def test_divide(self):

        self.assertEqual(divide(10, 2), 5)

        with self.assertRaises(ValueError):

            divide(10, 0)

if __name__ == '__main__':

    unittest.main()

Run the tests:

python test_math_operations.py

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Using pytest (Popular Third-Party Framework)

1. Install pytest:

pip install pytest

2. Write test cases in a simple, plain function format.

Example:

from math_operations import add, divide

def test_add():

    assert add(2, 3) == 5

    assert add(-1, 1) == 0

def test_divide():

    assert divide(10, 2) == 5

    try:

        divide(10, 0)

    except ValueError:

        pass

Run the tests:

pytest test_math_operations.py

Pytest automatically discovers test files prefixed with test_ and runs them.

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3. Write Assertions

Assertions are the core of unit tests. They check the expected outcome against the actual outcome.

Examples of assertions:

self.assertEqual(actual, expected)    # Check equality

self.assertTrue(condition)           # Check if condition is True

self.assertRaises(Exception, func)   # Check if exception is raised

Pytest equivalents:

assert actual == expected

with pytest.raises(Exception):

    func()

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4. Mocking External Dependencies

If your function interacts with external systems (e.g., APIs, databases), use the unittest.mock library to simulate their behavior.

Example with Mocking:

from unittest.mock import patch

import requests

def fetch_data(url):

    response = requests.get(url)

    return response.json()

@patch('requests.get')

def test_fetch_data(mock_get):

    mock_get.return_value.json.return_value = {"key": "value"}

    result = fetch_data("http://example.com")

    assert result == {"key": "value"}

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5. Test Coverage

To measure how much of your code is tested, use the coverage tool:

1. Install coverage:

pip install coverage

2. Run your tests with coverage:

coverage run -m pytest

3. Generate a coverage report:

coverage report -m

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6. Run Tests Automatically

Integrate unit tests into CI/CD pipelines using Jenkins, GitHub Actions, or GitLab CI/CD.

Example Jenkins Pipeline Stage:

stage('Run Unit Tests') {

    steps {

        sh 'pytest --junitxml=results.xml'

    }

}

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Would you like an example for testing a specific type of function, like API calls or database operations?

( Article enerated using chatgpt)