Testing Python programs with unittest

fizzbuzz.py

import unittest

class FizzBuzzException(Exception):
    pass

def fizz_buzz(param):
    result = ""
    try:
        variable = int(param)
    except ValueError:
        raise FizzBuzzException("This value is invalid")
    
    if variable % 3 == 0:
        result += "Fizz"
    if variable % 5 == 0:
        result += "Buzz"
    return result


class FizzBuzzTestCase(unittest.TestCase):
    def test_multiples_of_three_return_Fizz(self):
        result = fizz_buzz(3)
        self.assertEqual("Fizz", result)

    def test_multiples_of_five_returns_Buzz(self):
        result = fizz_buzz(5)
        self.assertEqual("Buzz", result)

    def test_multiples_of_fifteen_returns_FizzBuzz(self):
        result = fizz_buzz(15)
        self.assertEqual("FizzBuzz", result)

    def test_when_strings_are_passed(self):
        result = fizz_buzz("3")
        self.assertEqual(result, "Fizz")
        result = fizz_buzz("15")
        self.assertEqual(result, "FizzBuzz")
        with self.assertRaises(FizzBuzzException) as context:
            result = fizz_buzz("nonsense")
        self.assertEqual("This value is invalid", str(context.exception))


# if __name__ == '__main__':
#     unittest.

github_api.py

import requests
import unittest
from unittest import mock


class Rexception(Exception):
    pass


def make_call():
    response = requests.get('https://api.github.com/users')
    # import pdb
    # pdb.set_trace()
    if response.status_code < 400:
        result = response.json()
        if len(result) > 0:
            return result[0]
        return None
    else:
        raise Rexception(response.json()['error'])
    return None




class MockClass(object):
    def __init__(self, result, status_code):
        self.status_code = status_code
        self.result = result

    def json(self):
        return self.result


class RequestTestCase(unittest.TestCase):
    def setUp(self):
        self.patcher = mock.patch('requests.get')
        self.mock_get = self.patcher.start()

    def tearDown(self):
        self.patcher.stop()

    def test_api_call(self):
        self.mock_get.return_value = MockClass([
            {
                "login": "pjhyett",
                "id": 3,
                "avatar_url": "https://avatars0.githubusercontent.com/u/3?v=4",
                "gravatar_id": "",
            },
            {
                "login": "biola",
                "id": 4,
                "avatar_url": "https://avatars2.githubusercontent.com/u/3?v=4",
                "gravatar_id": "hello",
            }
        ], status_code=200)
        response = make_call()
        self.assertEqual(response, {
            "login": "pjhyett",
            "id": 3,
            "avatar_url": "https://avatars0.githubusercontent.com/u/3?v=4",
            "gravatar_id": "",
        })
        self.mock_get.assert_called_once_with('https://api.github.com/users')

    def test_api_call_2(self):
        self.mock_get.return_value = MockClass([

        ], status_code=200)
        response = make_call()
        self.assertEqual(response, None)
        self.mock_get.assert_called_once_with('https://api.github.com/users')

    def test_api_call_failed(self):
        self.mock_get.return_value = MockClass(
            {'error': "Connection error"}, status_code=400)
        with self.assertRaises(Rexception) as context:
            response = make_call()
        self.assertEqual("Connection error", str(context.exception))
        self.mock_get.assert_called_once_with('https://api.github.com/users')

If I wanted to use the default test runner to run the above tests, I need to ensure the names of each files begin with a test_*.py. So the fizzbuzz.py becomes test_fizzbuzz.py and the github_api.py becomes test_github_api.py

The command to run the tests (Assuming python 3) is
python -m unittest discover

If we want to use other test runners supported by python nose and pytest
For nose

$ pip install nose
$ nosetest 

For pytest

$ pip install pytest
$ py.test