Test-Driven Development with Python, 3rd Edition

Chapter 21. Using Mocks for Test Isolation

In this chapter, we’ll finish up our login system. While doing so, we’ll explore an alternative use of mocks: to isolate parts of the system from each other. This enables more targeted testing, fights combinatorial explosion, and reduces duplication between tests.

Note

In this chapter, we start to drift towards what’s called “London-school TDD”, which is a variant on the “Classical” or “Detroit” style of TDD that I mostly show in the book. We won’t get into the details here, but London-school TDD places more emphasis on mocking and isolating parts of the system. As always, there are pros and cons! Read more at Online Appendix: Test Isolation and “Listening to Your Tests”.

Along the way, we’ll learn a few more useful features of unittest.mock, and we’ll also have a discussion about how many tests are “enough”.

Using Our Auth Backend in the Login View

• Token model with email and UID

• View to create token and send login email incl. url w/ token UID

• Custom user model with USERNAME_FIELD=email

• Authentication backend with authenticate() and get_user() functions

• Registering auth backend in settings.py

• Login view calls authenticate() and login() from django.contrib.auth

• Logout view calls django.contrib.auth.logout

We got our auth backend ready in the last chapter; now we need use the backend in our login view. But first, as our scratchpad says, we need to add it to settings.py:

src/superlists/settings.py (ch21l001)

AUTH_USER_MODEL ...