> In Section 8.4.2, we verified by hand that the persistent session implemented in the preceding sections is working, but in fact the relevant branch in the current_user method is currently completely untested. My favorite way to handle this kind of situation is to raise an exception in the suspected untested block of code: if the code isn’t covered, the tests will still pass; if it is covered, the resulting error will identify the relevant test. У - удобно.