Python testing

Talk presented at Python Lima meetup

Transcript

1. Testing in Python Testing in Python - Erick Navarro - @erickgnavar 1
2. Who am I? >>> import erick { "full_name": "Erick Navarro", "email": "erick@navarro.io", "twitter": "@erickgnavar" } Testing in Python - Erick Navarro - @erickgnavar 2
3. http://www.commitstrip.com/en/2017/02/08/where-are-the-tests/
4. http://www.commitstrip.com/en/2013/10/11/mieux-et-moins-cher-que-les-tests-unitaires/
5. Why don't we do tests? Testing in Python - Erick Navarro - @erickgnavar 5
6. Why don't we do tests? 4 Lazyness Testing in Python - Erick Navarro - @erickgnavar 5
7. Why don't we do tests? 4 Lazyness 4 Deadlines Testing in Python - Erick Navarro - @erickgnavar 5
8. Why don't we do tests? 4 Lazyness 4 Deadlines 4 Think they are useless Testing in Python - Erick Navarro - @erickgnavar 5
9. Code without tests is broken as designed. 1 Jacob Kaplan-Moss Testing in Python - Erick Navarro - @erickgnavar 6
10. Why testing? Testing in Python - Erick Navarro - @erickgnavar 7
11. Why testing? 4 Ensure code behaviour Testing in Python - Erick Navarro - @erickgnavar 7
12. Why testing? 4 Ensure code behaviour 4 To be sure (mostly) your changes don't break other modules Testing in Python - Erick Navarro - @erickgnavar 7
13. Why testing? 4 Ensure code behaviour 4 To be sure (mostly) your changes don't break other modules 4 Notice bugs "easily" Testing in Python - Erick Navarro - @erickgnavar 7
14. Why testing? 4 Ensure code behaviour 4 To be sure (mostly) your changes don't break other modules 4 Notice bugs "easily" 4 Make maintainable software Testing in Python - Erick Navarro - @erickgnavar 7
15. Why testing? 4 Ensure code behaviour 4 To be sure (mostly) your changes don't break other modules 4 Notice bugs "easily" 4 Make maintainable software 4 Be kind with future developers Testing in Python - Erick Navarro - @erickgnavar 7
16. Some terms you might have heard about Testing in Python - Erick Navarro - @erickgnavar 8
17. Some terms you might have heard about 4 Unit test Testing in Python - Erick Navarro - @erickgnavar 8
18. Some terms you might have heard about 4 Unit test 4 Integration test Testing in Python - Erick Navarro - @erickgnavar 8
19. Some terms you might have heard about 4 Unit test 4 Integration test 4 TDD Testing in Python - Erick Navarro - @erickgnavar 8
20. Some terms you might have heard about 4 Unit test 4 Integration test 4 TDD 4 BDD Testing in Python - Erick Navarro - @erickgnavar 8
21. Some terms you might have heard about 4 Unit test 4 Integration test 4 TDD 4 BDD 4 Mock Testing in Python - Erick Navarro - @erickgnavar 8
22. Some terms you might have heard about 4 Unit test 4 Integration test 4 TDD 4 BDD 4 Mock 4 Stubs Testing in Python - Erick Navarro - @erickgnavar 8
23. Some terms you might have heard about 4 Unit test 4 Integration test 4 TDD 4 BDD 4 Mock 4 Stubs 4 Coverage Testing in Python - Erick Navarro - @erickgnavar 8
24. So much to learn! Testing in Python - Erick Navarro - @erickgnavar 9
25. So much to learn! Testing in Python - Erick Navarro - @erickgnavar 10
26. Start simple! Testing in Python - Erick Navarro - @erickgnavar 11
27. # simple_test.py def sum(a, b): return a + b assert sum(1, 2) == 3, "Your math is wrong!" Run the "test" $ python simple_test.py Testing in Python - Erick Navarro - @erickgnavar 12
28. Some examples Testing in Python - Erick Navarro - @erickgnavar 13
29. Dummy test case # test_dummy.py import unittest class DummyTestCase(unittest.TestCase): def test_dummy(self): self.assertEqual(1, 1) Testing in Python - Erick Navarro - @erickgnavar 14
30. Dummy test case # test_dummy.py import unittest class DummyTestCase(unittest.TestCase): def test_dummy(self): self.assertEqual(1, 1) Testing in Python - Erick Navarro - @erickgnavar 14
31. Dummy test case # test_dummy.py import unittest class DummyTestCase(unittest.TestCase): def test_dummy(self): self.assertEqual(1, 1) Testing in Python - Erick Navarro - @erickgnavar 14
32. Dummy test case # test_dummy.py import unittest class DummyTestCase(unittest.TestCase): def test_dummy(self): self.assertEqual(1, 1) Testing in Python - Erick Navarro - @erickgnavar 14
33. Dummy test case # test_dummy.py import unittest class DummyTestCase(unittest.TestCase): def test_dummy(self): self.assertEqual(1, 1) Testing in Python - Erick Navarro - @erickgnavar 14
34. Dummy test case # test_dummy.py import unittest class DummyTestCase(unittest.TestCase): def test_dummy(self): self.assertEqual(1, 1) Testing in Python - Erick Navarro - @erickgnavar 14
35. Running the test python -m unittest . ---------------------------------------------------------------------- Ran 1 test in 0.001s OK Testing in Python - Erick Navarro - @erickgnavar 15
36. Our first test! Testing in Python - Erick Navarro - @erickgnavar 16
37. Let's make a more elaborate example Testing in Python - Erick Navarro - @erickgnavar 17
38. An evil beer module Testing in Python - Erick Navarro - @erickgnavar 18
39. # beer.py def fetch_weather(city): # make a request to some API def calculate_beer_price(): temp = fetch_weather("Lima") if temp > 25.0: return 10.5 else: return 8.0 Testing in Python - Erick Navarro - @erickgnavar 19
40. # beer.py def fetch_weather(city): # make a request to some API def calculate_beer_price(): temp = fetch_weather("Lima") if temp > 25.0: return 10.5 else: return 8.0 Testing in Python - Erick Navarro - @erickgnavar 19
41. # beer.py def fetch_weather(city): # make a request to some API def calculate_beer_price(): temp = fetch_weather("Lima") if temp > 25.0: return 10.5 else: return 8.0 Testing in Python - Erick Navarro - @erickgnavar 19
42. # beer.py def fetch_weather(city): # make a request to some API def calculate_beer_price(): temp = fetch_weather("Lima") if temp > 25.0: return 10.5 else: return 8.0 Testing in Python - Erick Navarro - @erickgnavar 19
43. # beer.py def fetch_weather(city): # make a request to some API def calculate_beer_price(): temp = fetch_weather("Lima") if temp > 25.0: return 10.5 else: return 8.0 Testing in Python - Erick Navarro - @erickgnavar 19
44. We can't control the weather Testing in Python - Erick Navarro - @erickgnavar 20
45. Mocking to the rescue Testing in Python - Erick Navarro - @erickgnavar 21
46. Simple example from unittest import mock @mock.patch("utils.sum") def test_dummy(self, mock_sum): mock_sum.return_value = 10 value = sum(1, 2) self.assertEqual(value, 10) Testing in Python - Erick Navarro - @erickgnavar 22
47. Simple example from unittest import mock @mock.patch("utils.sum") def test_dummy(self, mock_sum): mock_sum.return_value = 10 value = sum(1, 2) self.assertEqual(value, 10) Testing in Python - Erick Navarro - @erickgnavar 22
48. Simple example from unittest import mock @mock.patch("utils.sum") def test_dummy(self, mock_sum): mock_sum.return_value = 10 value = sum(1, 2) self.assertEqual(value, 10) Testing in Python - Erick Navarro - @erickgnavar 22
49. Simple example from unittest import mock @mock.patch("utils.sum") def test_dummy(self, mock_sum): mock_sum.return_value = 10 value = sum(1, 2) self.assertEqual(value, 10) Testing in Python - Erick Navarro - @erickgnavar 22
50. Simple example from unittest import mock @mock.patch("utils.sum") def test_dummy(self, mock_sum): mock_sum.return_value = 10 value = sum(1, 2) self.assertEqual(value, 10) Testing in Python - Erick Navarro - @erickgnavar 22
51. Simple example from unittest import mock @mock.patch("utils.sum") def test_dummy(self, mock_sum): mock_sum.return_value = 10 value = sum(1, 2) self.assertEqual(value, 10) Testing in Python - Erick Navarro - @erickgnavar 22
52. Testing beer.py # test_beer.py import unittest from unittest import mock from beer import calculate_beer_price class BeerTestCase(unittest.TestCase): def test_calculate_price_on_sunny_day(self): ... def test_calculate_price_on_cloudy_day(self): ... Testing in Python - Erick Navarro - @erickgnavar 23
53. Testing beer.py # test_beer.py import unittest from unittest import mock from beer import calculate_beer_price class BeerTestCase(unittest.TestCase): def test_calculate_price_on_sunny_day(self): ... def test_calculate_price_on_cloudy_day(self): ... Testing in Python - Erick Navarro - @erickgnavar 23
54. Testing beer.py # test_beer.py import unittest from unittest import mock from beer import calculate_beer_price class BeerTestCase(unittest.TestCase): def test_calculate_price_on_sunny_day(self): ... def test_calculate_price_on_cloudy_day(self): ... Testing in Python - Erick Navarro - @erickgnavar 23
55. Testing beer.py # test_beer.py import unittest from unittest import mock from beer import calculate_beer_price class BeerTestCase(unittest.TestCase): def test_calculate_price_on_sunny_day(self): ... def test_calculate_price_on_cloudy_day(self): ... Testing in Python - Erick Navarro - @erickgnavar 23
56. Testing beer.py # test_beer.py import unittest from unittest import mock from beer import calculate_beer_price class BeerTestCase(unittest.TestCase): def test_calculate_price_on_sunny_day(self): ... def test_calculate_price_on_cloudy_day(self): ... Testing in Python - Erick Navarro - @erickgnavar 23
57. Testing beer.py # test_beer.py import unittest from unittest import mock from beer import calculate_beer_price class BeerTestCase(unittest.TestCase): def test_calculate_price_on_sunny_day(self): ... def test_calculate_price_on_cloudy_day(self): ... Testing in Python - Erick Navarro - @erickgnavar 23
58. Testing beer.py # test_beer.py import unittest from unittest import mock from beer import calculate_beer_price class BeerTestCase(unittest.TestCase): def test_calculate_price_on_sunny_day(self): ... def test_calculate_price_on_cloudy_day(self): ... Testing in Python - Erick Navarro - @erickgnavar 23
59. @mock.patch("beer.fetch_weather") def test_calculate_price_on_sunny_day(self, mock_fetch_weather): mock_fetch_weather.return_value = 30 price = calculate_beer_price() self.assertEqual(price, 10.5) @mock.patch("beer.fetch_weather") def test_calculate_price_on_cloudy_day(self, mock_fetch_weather): mock_fetch_weather.return_value = 15 price = calculate_beer_price() self.assertEqual(price, 8.0) Testing in Python - Erick Navarro - @erickgnavar 24
60. @mock.patch("beer.fetch_weather") def test_calculate_price_on_sunny_day(self, mock_fetch_weather): mock_fetch_weather.return_value = 30 price = calculate_beer_price() self.assertEqual(price, 10.5) @mock.patch("beer.fetch_weather") def test_calculate_price_on_cloudy_day(self, mock_fetch_weather): mock_fetch_weather.return_value = 15 price = calculate_beer_price() self.assertEqual(price, 8.0) Testing in Python - Erick Navarro - @erickgnavar 24
61. @mock.patch("beer.fetch_weather") def test_calculate_price_on_sunny_day(self, mock_fetch_weather): mock_fetch_weather.return_value = 30 price = calculate_beer_price() self.assertEqual(price, 10.5) @mock.patch("beer.fetch_weather") def test_calculate_price_on_cloudy_day(self, mock_fetch_weather): mock_fetch_weather.return_value = 15 price = calculate_beer_price() self.assertEqual(price, 8.0) Testing in Python - Erick Navarro - @erickgnavar 24
62. @mock.patch("beer.fetch_weather") def test_calculate_price_on_sunny_day(self, mock_fetch_weather): mock_fetch_weather.return_value = 30 price = calculate_beer_price() self.assertEqual(price, 10.5) @mock.patch("beer.fetch_weather") def test_calculate_price_on_cloudy_day(self, mock_fetch_weather): mock_fetch_weather.return_value = 15 price = calculate_beer_price() self.assertEqual(price, 8.0) Testing in Python - Erick Navarro - @erickgnavar 24
63. @mock.patch("beer.fetch_weather") def test_calculate_price_on_sunny_day(self, mock_fetch_weather): mock_fetch_weather.return_value = 30 price = calculate_beer_price() self.assertEqual(price, 10.5) @mock.patch("beer.fetch_weather") def test_calculate_price_on_cloudy_day(self, mock_fetch_weather): mock_fetch_weather.return_value = 15 price = calculate_beer_price() self.assertEqual(price, 8.0) Testing in Python - Erick Navarro - @erickgnavar 24
64. @mock.patch("beer.fetch_weather") def test_calculate_price_on_sunny_day(self, mock_fetch_weather): mock_fetch_weather.return_value = 30 price = calculate_beer_price() self.assertEqual(price, 10.5) @mock.patch("beer.fetch_weather") def test_calculate_price_on_cloudy_day(self, mock_fetch_weather): mock_fetch_weather.return_value = 15 price = calculate_beer_price() self.assertEqual(price, 8.0) Testing in Python - Erick Navarro - @erickgnavar 24
65. @mock.patch("beer.fetch_weather") def test_calculate_price_on_sunny_day(self, mock_fetch_weather): mock_fetch_weather.return_value = 30 price = calculate_beer_price() self.assertEqual(price, 10.5) @mock.patch("beer.fetch_weather") def test_calculate_price_on_cloudy_day(self, mock_fetch_weather): mock_fetch_weather.return_value = 15 price = calculate_beer_price() self.assertEqual(price, 8.0) Testing in Python - Erick Navarro - @erickgnavar 24
66. @mock.patch("beer.fetch_weather") def test_calculate_price_on_sunny_day(self, mock_fetch_weather): mock_fetch_weather.return_value = 30 price = calculate_beer_price() self.assertEqual(price, 10.5) @mock.patch("beer.fetch_weather") def test_calculate_price_on_cloudy_day(self, mock_fetch_weather): mock_fetch_weather.return_value = 15 price = calculate_beer_price() self.assertEqual(price, 8.0) Testing in Python - Erick Navarro - @erickgnavar 24
67. There is a problem Testing in Python - Erick Navarro - @erickgnavar 25
68. No internet access Testing in Python - Erick Navarro - @erickgnavar 26
69. Let's fix the problem! Testing in Python - Erick Navarro - @erickgnavar 27
70. # beer.py v2 def fetch_weather(city): """Returns None if there is no network""" # make a request to some API def calculate_beer_price(): temp = fetch_weather("Lima") if temp is None: return 9.0 elif temp > 25.0: return 10.5 else: return 8.0 Testing in Python - Erick Navarro - @erickgnavar 28
71. # beer.py v2 def fetch_weather(city): """Returns None if there is no network""" # make a request to some API def calculate_beer_price(): temp = fetch_weather("Lima") if temp is None: return 9.0 elif temp > 25.0: return 10.5 else: return 8.0 Testing in Python - Erick Navarro - @erickgnavar 28
72. # beer.py v2 def fetch_weather(city): """Returns None if there is no network""" # make a request to some API def calculate_beer_price(): temp = fetch_weather("Lima") if temp is None: return 9.0 elif temp > 25.0: return 10.5 else: return 8.0 Testing in Python - Erick Navarro - @erickgnavar 28
73. Testing beer.py v2 import unittest from unittest import mock from beer import calculate_beer_price class BeerTestCase(unittest.TestCase): def test_calculate_price_on_sunny_day(self): ... def test_calculate_price_on_cloudy_day(self): ... def test_calculate_price_with_no_weather(self): ... Testing in Python - Erick Navarro - @erickgnavar 29
74. Testing side effects @mock.patch("beer.fetch_weather") def test_calculate_price_with_no_weather(self, mock_fetch_weather): mock_fetch_weather.side_effect = NetworkError() price = calculate_beer_price() self.assertEqual(price, 9.0) Testing in Python - Erick Navarro - @erickgnavar 30
75. Testing side effects @mock.patch("beer.fetch_weather") def test_calculate_price_with_no_weather(self, mock_fetch_weather): mock_fetch_weather.side_effect = NetworkError() price = calculate_beer_price() self.assertEqual(price, 9.0) Testing in Python - Erick Navarro - @erickgnavar 30
76. Testing side effects @mock.patch("beer.fetch_weather") def test_calculate_price_with_no_weather(self, mock_fetch_weather): mock_fetch_weather.side_effect = NetworkError() price = calculate_beer_price() self.assertEqual(price, 9.0) Testing in Python - Erick Navarro - @erickgnavar 30
77. Testing side effects @mock.patch("beer.fetch_weather") def test_calculate_price_with_no_weather(self, mock_fetch_weather): mock_fetch_weather.side_effect = NetworkError() price = calculate_beer_price() self.assertEqual(price, 9.0) Testing in Python - Erick Navarro - @erickgnavar 30
78. Testing side effects @mock.patch("beer.fetch_weather") def test_calculate_price_with_no_weather(self, mock_fetch_weather): mock_fetch_weather.side_effect = NetworkError() price = calculate_beer_price() self.assertEqual(price, 9.0) Testing in Python - Erick Navarro - @erickgnavar 30
79. Now it looks better Testing in Python - Erick Navarro - @erickgnavar 31
80. Final thoughts Testing in Python - Erick Navarro - @erickgnavar 32
81. Final thoughts 4 We don't have to test the whole application Testing in Python - Erick Navarro - @erickgnavar 32
82. Final thoughts 4 We don't have to test the whole application 4 Testing helps you to do better code Testing in Python - Erick Navarro - @erickgnavar 32
83. Final thoughts 4 We don't have to test the whole application 4 Testing helps you to do better code 4 100% test coverage doesn't ensure the code is free of bugs Testing in Python - Erick Navarro - @erickgnavar 32
84. Final thoughts 4 We don't have to test the whole application 4 Testing helps you to do better code 4 100% test coverage doesn't ensure the code is free of bugs 4 One test at time Testing in Python - Erick Navarro - @erickgnavar 32
85. Resources 4 https://realpython.com/python-testing/ 4 https://docs.python.org/3/library/unittest.html 4 https://docs.pytest.org/en/latest/ Testing in Python - Erick Navarro - @erickgnavar 33
86. Questions? Testing in Python - Erick Navarro - @erickgnavar 34
87. Thanks Testing in Python - Erick Navarro - @erickgnavar 35