Pytest/Unittest: Listing common cases in Testing your Code

Testing Checklist

Pytest & Unittest Common Cases

Introduction

Many articles have already been written about Pytest and unittest. This guide serves as a quick checklist or a reference for common situations you'll encounter while testing your Python code.

Unittest

Available natively in Python. Inspired by JUnit, it follows the xUnit style where test cases are organized into classes derived from unittest.TestCase.

Pytest

A popular third-party framework that makes testing simpler and more expressive. It supports fixtures, plain assert statements, and powerful parameterization.

Installation

terminal

python -m pip install pytest pytest-mock requests requests_mock

Common Cases

1. Using requests_mock as a Context Manager

import requests_mock
from main import process_get_request

def test_process_get_request():
    url = 'https://api.github.com'
    with requests_mock.Mocker() as mocker:
        mock_response = {"key": "value"}
        mocker.get(url, json=mock_response, status_code=200)
        result = process_get_request(url)
        assert result == {"key": "value"}

2. Using the Mocker Fixture

def test_process_get_request_with_mocker(mocker):
    mock_response = mocker.Mock(status_code=200)
    mock_response.json.return_value = {"key": "value"}
    mocker.patch("requests.get", return_value=mock_response)
    result = process_get_request('https://api.github.com')
    assert result == {"key": "value"}

3. Parameterize for Multiple Scenarios

@pytest.mark.parametrize(
    "url, expected_status, expected_result",
    [
        ("https://api.github.com/data", 200, {"key": "value"}),
        ("https://api.github.com/404", 404, None),
    ],
)
def test_process_get_request(url, expected_status, expected_result):
    with requests_mock.Mocker() as mocker:
        mocker.get(url, json=expected_result, status_code=expected_status)
        result = process_get_request(url)
        assert result == expected_result

4. Patching Methods with patch.object

def test_search_repo_with_patch_object():
    search_repo_obj = SearchRepo()
    with unittest.mock.patch.object(search_repo_obj, "call_http_class") as mock_call:
        mock_call.return_value = {"repos": ["repo1", "repo2"]}
        result = search_repo_obj.search_repo_with_name('url', "repo2")
        assert result is True

5. Testing if an Exception occurred

def test_exception_raised():
    with pytest.raises(ValueError, match="No response received from the API"):
        trigger_error_condition()

Until then, your friend here, Hemachandra, is signing off…

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