March 2017
Intermediate to advanced
442 pages
10h 44m
English
Content preview from Refactoring JavaScript
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Chapter 4. Testing in Action
In the last chapter, we looked at some common objections to testing, and explored the benefits that can hopefully overwhelm those objections. If they can’t for your project, then there’s a strong possibility that either your team doesn’t have the strongest engineering culture (quite possibly for reasons out of their control), or you haven’t quite turned the corner on being able to write tests fast enough to justify their benefits.
In this chapter, we’re getting into the details of how to test in the following scenarios:
- New code from scratch
- New code from scratch with TDD
- New features
- Untested code
- Debugging and regression tests
At the risk of beating a dead horse, you can’t refactor without tests. You can change code, but you need a way to guarantee that your code paths are working.
Refactoring without tests: A historical note
In the original 1992 work on refactoring, “Refactoring Object-Oriented Frameworks” by William Opdyke (and advised by Ralph Johnson of “Design Patterns” fame), the word test appears only 39 times in a 202-page paper. However, Opdyke is insistent on refactoring as a process that preserves behavior. The term invariant appears 125 times, and precondition comes up frequently as well.
In a nonacademic setting, 25 years after the original work, and in JavaScript, with its rich ecosystem of testing tools, the mechanisms of preserving behavior are best facilitated by the processes we discuss in this book, and especially this chapter. ...
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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.