Mock - Mocking and Testing Library, A Lightening Talk

This is a simple presentation on mock. Its meant to be a quick introduction to using mock in when writing your unit tests.

Transcript

1. Mock - Mocking and Testing Library
2. About me { “name”: “Burton Williams”, “title”: “Software Engineer Contractor”, “email” : “burton.b.williams@gmail.com”, “github” : “ikiini”, “country”: “St Vincent and the Grenadines” }
3. What is Mock? “Mock is a library for testing in Python. It allows you to replace parts of your system under test with mock objects and make assertions about how they have been used”
4. Creating a Mock Object >>> from mock import Mock >>> my_mock_object = Mock()
5. How do I use my mock object? >>> instance_of_my_mock = my_mock_object() Or >>> instance_of_my_mock = \ my_mock_object.return_value
6. How do I use my mock object? >>> import db >>> class MyMarvelousClass(object): ... def sum_transactions(self): ... total = 0 ... for transaction in db.transactions.find({},{'total':1}): ... total += transaction['total'] ... return total >>> class MyMarvelousClassTestCase(unittest.TestCase): ... def test_add(self): ... mock_db = Mock() ... mock_db_instance = mock_db() # or mock_db.return_value ... mock_db_instance.transactions.find.return_value = [{'total' :1}, {'total' :2}, {'total' :5}] ... marvelous = MyMarvelousClass() ... marvelous.db = mock_db_instance ... result = class.sum_transactions() ... self.assertEqual(result, 8)
7. How do I use my mock object? >>>@patch.object('module_name.object_to_replace_with_mock') ... class MyMarvelousClassTestCase(unittest.TestCase): ... def test_add(self, mock_db): ... marvelous = MyMarvelousClass() ... mock_db_instance = mock_db.return_value ... mock_db_instance.transactions.find.return_value = [{'total' :1}, {'total' :2}, {'total' :5}] ... marvelous.db = mock_db_instance ... result = class.sum_transactions() ... self.assertEqual(result, 8) ... def test_add(self, mock_db): ... instance = mock_db.return_value
8. Other things you can do with Mock • side_effect – Return different values, either controlled or varied by writing a function and assigning it to side_effect variable of mock instance. • mock_calls – Assert what methods were called.
9. Mock Docs. http://www.voidspace.org.uk/python/mock/index.html
10. Thank you!