Testing¶
Note
The below examples are in Python, but the concepts apply to testing in any language.
See also
Looking for OSF-specific testing guidelines? See the Testing the OSF page.
General Testing Guidelines¶
- Use long, descriptive names. This often obviates the need for doctrings in test methods. This also makes it easier to locate tests that fail.
- Tests should be isolated. Don’t interact with a real database or network. Use a separate test database that gets torn down or use mock objects.
- Prefer factories to fixtures.
- Never let incomplete tests pass, else you run the risk of forgetting about them. Instead, add a placeholder like
assert False, "TODO: finish me". If you are stubbing out a test that will be written in the future, use the@unittest.skip()decorator. - Strive for 100% code coverage, but don’t get obsess over coverage scores.
- When testing the contents of a dictionary, test the keys individually.
# Yes
assert_equal(result['foo'], 42)
assert_equal(result['bar'], 24)
# No
assert_equal(result, {'foo': 42, 'bar': 24})
Unit Tests¶
- Focus on one tiny bit of functionality.
- Should be fast, but a slow test is better than no test.
- It often makes sense to have one testcase class for a single class or model.
import unittest
import factories
class PersonTest(unittest.TestCase):
def setUp(self):
self.person = factories.PersonFactory()
def test_has_age_in_dog_years(self):
assert self.person.dog_years == self.person.age / 7
Functional Tests¶
Functional tests are higher level tests that are closer to how an end-user would interact with your application. They are typically used for web and GUI applications.
- Write tests as scenarios. Testcase and test method names should read like a scenario description.
- Use comments to write out stories, before writing the test code.
class TestAUser(unittest.TestCase):
def test_can_write_a_blog_post(self):
# Goes to the her dashboard
...
# Clicks "New Post"
...
# Fills out the post form
...
# Clicks "Submit"
...
# Can see the new post
...
Notice how the testcase and test method read together like “Test A User can write a blog post”.
Supporting Libraries¶
Python¶
- nose: Extends Python’s unittest. Includes a test runner and various utilities.
- pytest: A powerful test runner and library for writing automated tests.
- factory-boy: Utility library for creating test objects. Replaces fixtures with “factories”.
- mock: Allows you to mock and patch objects for testing purposes.
- webtest / webtest-plus : Provides a
TestAppwith which to send test requests and make assertions about the responses. - faker : A fake data generator.