October 2021
Intermediate to advanced
277 pages
5h 48m
English
Content preview from Learning Test-Driven Development
Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.
Chapter 11. Banking on Redesign
On the whole it’s worth evolving your design as your needs grow…1Martin Fowler, Patterns of Enterprise Application Architecture (Addison-Wesley, 2002)
We introduced the Portfolio entity back in Chapter 3. It represents a key concept from our domain, so we’re justified in giving it some responsibility. Now, our Portfolio does too much work and it shows. Its primary job is to be a repository of Money entities. However, it has taken on the added responsibility of converting between currencies. To do this, it has to hold on to an exchange rate table and the logic to do the conversion. This doesn’t look like the responsibility of a Portfolio. Monetary conversion has as much business being in a portfolio as peanut butter has being on top of a pizza.
Our software program has grown along with our needs. It is worth improving our design and looking for a better abstraction than the shoved-in way conversion between currencies is currently implemented.
A principle of domain-driven design (DDD) is continuous learning. When we learn something new about our domain, we let our design reflect our acquired knowledge. The resulting design and software should reflect our improved understanding of our domain.
Tip
Domain-driven design is a discipline that’s ably supported by TDD. Eric Evans’ book of the same title is the seminal work on the subject.
By implementing currency conversion over the last few chapters, we have gained fresh insight into our program. It’s ...
Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
and much more.
Read now
Unlock full access
More than 5,000 organizations count on O’Reilly
O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.