Test-Driven Development with Python, 3rd Edition

Chapter 7. Working Incrementally

A Note for Early Release Readers

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This will be the 7th chapter of the final book. The GitHub repo is available at https://github.com/hjwp/book-example.

If you have comments about how we might improve the content and/or examples in this book, or if you notice missing material within this chapter, please reach out to the author at [e-mail].

Now let’s address our real problem, which is that our design only allows for one global list. In this chapter I’ll demonstrate a critical TDD technique: how to adapt existing code using an incremental, step-by-step process which takes you from working state to working state. Testing Goat, not Refactoring Cat!

Small Design When Necessary

Let’s have a think about how we want support for multiple lists to work.

At the moment the only URL for our site is the homepage, and that’s why there’s only one global list. The most obvious way to support multiple lists is to say that each list gets its own URL, so that people can start multiple lists, or so that different people can have different lists. How might that work?

Not Big Design Up Front

TDD is closely associated with the agile movement in software development, which includes a reaction against Big Design Up Front, the traditional ...