Test-Driven Development with Python, 3rd Edition

Chapter 6. Improving Functional Tests: Ensuring Isolation and Removing Magic Sleeps

Before we dive in and fix our single-global-list problem, let’s take care of a couple of housekeeping items. At the end of the last chapter, we made a note that different test runs were interfering with each other, so we’ll fix that. I’m also not happy with all these time.sleeps peppered through the code; they seem a bit unscientific, so we’ll replace them with something more reliable:

• Clean up after FT runs.

• Remove time.sleeps.

Both of these changes will be moving us towards testing “best practices”, making our tests more deterministic and more reliable.

Ensuring Test Isolation in Functional Tests

We ended the last chapter with a classic testing problem: how to ensure isolation between tests. Each run of our functional tests (FTs) left list items lying around in the database, and that interfered with the test results when next running the tests.

When we run unit tests, the Django test runner automatically creates a brand new test database (separate from the real one), which it can safely reset before each individual test is run, and then thrown away at the end. But our FTs currently run against the “real” database, db.sqlite3.

One way to tackle this would be to “roll our own” solution, and add some code to functional_tests.py, which would do the cleaning up. The setUp and tearDown methods are perfect for this sort of thing.

But as this is a common problem, Django supplies a test ...