You face a problem with your code. Maybe something is bugging you about the design approach. Or maybe you’re just plain stuck. What can you do to break through a mental block?
During one job interview, I remember asking how the candidate approached problem solving. That candidate’s answer has stuck with me over the years:
You’re building a new network call to a server. The thing that will actually use this call isn’t ready. But you’re anxious to see the call work in a full round-trip to the actual server. Basically, you want to know: does this part of the code work? How can you get the feedback you need?
Answer: Quickly hack together any way that works.
The agile workflow is to build, validate, and adjust course. Extreme Programming teaches us to use many feedback loops. And fast feedback is the primary benefit of TDD. …But TDD isn’t the only way I’ve gotten feedback on my Marvel Browser:
This time, I want to combine these two approaches. It’s a hybrid for which I don’t have a name. Maybe a “spike test”?[This post is part of the series TDD Sample App: The Complete Collection …So Far]
A Value Object is a handy way to combine multiple values in a single object. It sounds simple — you just make each value a property, right? Well, there’s usually more to it than that. There’s even an entire objc.io article about Value Objects. …So how do you define a new Value Object?
I believe in laziness. Let’s do as little work as possible!
Objects are like horses. The less they know about their chaotic surroundings, the easier it is to control them.
We don’t want our objects to be spooked when there’s a lot going on. So let’s build ignorance into our systems.
But how? We typically write mobile apps with these things at the center:
These frameworks bore into our apps like warts with deep roots. Web-centric, UI-centric, and persistence-centric knowledge spreads through our apps, making our code tightly coupled. And then we wonder why it’s hard to write unit tests!
Is there an alternative?
Robert Martin’s Clean Architecture offers a different way. Instead of being at the core, things like web communication and even the UI can become plug-ins. They live at the edges of the app. Use cases and business logic become the center of the app.[This post is part of the series TDD Sample App: The Complete Collection …So Far]
When you’re hiking and don’t know which way to go, what should you do? Stop. Get your bearings.
The same applies to Test-Driven Development; sometimes you need to stop doing TDD, and get some answers.
Those answers can come by switching from clean code to a style of quick-and-dirty hacking called a “spike solution.” I explained the basic idea in How to TDD the Unknown with a Spike Solution.
But what does it look like in practice?
So you want to try Test-Driven Development — great! But that requires expressing the intent of the code-to-be in automated tests. Where should you start if you don’t even know what the code should do? What should you do if you’re not confident about a particular approach?
You drive a spike through it!
To start my “Marvel Browser” iOS TDD sample app, I want to begin by making a network call to the Marvel API. If I knew what I was doing, I would start the 3-step “TDD waltz” of writing a single failing test, then writing the simplest code that passes, then refactoring.
But there are two roadblocks keeping me from writing my first test:
objc.io is a monthly online magazine, with an editorial team. Each issue focuses on a particular subject, and Issue #15 is about Testing. I’m honored to be a contributor with my article “Dependency Injection”.
In the spirit of Dr. Seuss, this video begins,
When a coder sits down to start banging out code,
the first thing to start crowding his cognitive load
is whether his program will do what it should.
“Correctness,” he says, “is what makes my code good.”
But it goes on to explain why clean, readable code matters, and ways to get there…
For such a short video, it has a lot of meat. And I love that last sentence! I really should get a copy of the Kent Beck book that inspired it, Implementation Patterns. (Disclosure: This book link is an affiliate link. If you buy anything, I earn a commission, at no extra cost to you.)
Question: What did you think of the video? Leave a comment below.
What would you give to be able to improve your existing codebase with complete safety?
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The Refactoring book completely changed the way I code.
In 2001 while searching for information on design patterns, I discovered the original wiki, and stumbled on Extreme Programming. This led me to a software development conference in 2002 called SD West. There I attended a session by Martin Fowler, and knew that I had to pick up his Refactoring book that day.
How could I resist a book that promised to teach me about “improving the design of existing code”?