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What works and what doesn't work in software development? For the first 10 years or so of my career, we followed a strict waterfall development model. Then in 2008 we started switching to an agile development model. In 2011 we added DevOps principles and practices. Our product team has also become increasingly global. This blog is about our successes and failures, and what we've learned along the way.



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Monday, March 22, 2010

Is Shift-Left Agile? And Death By Build

Sometimes people confuse "shift-left" and "agile" software development practices. They both involve testing earlier, and talking to customers earlier, but that's pretty much all they have in common.

"Shift-left" practices are ones that help you find and fix problems earlier. You can think of the software development life cycle as a time line, with gathering requirements on the left, then design, code, test, and field maintenance to the right. The earlier (and farther to the left) you find a problem, the less it will cost you to fix it. It takes extra time and effort to find problems earlier, but it's worth it in the long run. For example, if you create JUnit test cases for most of your new code, you will invest more time up front, but you'll almost certainly find some bugs even before the code is handed off to the testers.

Showing your code-in-progress to customers on a regular basis is also a "shift-left" practice, because you may find out that you are not delivering what the customers want early enough to change your design.

"Shift-left" practices can help make your project more agile, because if you catch bugs earlier, you don't need to have such a long test cycle at the end of a release. If you automate your tests and run the automated tests with every build, you can also find newly-introduced bugs in old code more easily, and cut down on the amount of regression testing and bug-fixing you have to do later.

But you can slow down a project with "shift-left" processes too. I know of a project where their build process takes 30+ hours. I'm assuming it takes so long because they're trying to do too much automated code analysis and automated unit testing as part of the build process. (My product is quite large, requiring several CDs, and it only takes about an hour to build everything.) Then, after the 30-hour build, they start their BVT (build verification test), which also takes many hours. The goal of testing during the build process is to catch bugs that escaped unit test before they get to the test team, and "shift-left". But because the build process is so slow and painful, they only run it once a week! So if a code change misses a build, it's delayed by an entire week. And if someone's new code breaks the build (heaven forbid), the entire project is delayed by a week.

So what did they do to avoid accidentally delaying the project by a week? They implemented a heavy process of code reviews to make sure that no one integrates code that will break the build. Code reviews and inspections are another "shift-left" tool. So now you have to make your code changes by Wednesday. On Wednesday you have to find a team leader to review your code changes and approve them so they're ready for the Thursday build. Then the build and BVT processes run on Thursday, Friday, Saturday, and code is ready to be tested on Monday.

This is the opposite of an agile process. Yet, strangely enough, this team claims that they are following agile software development processes, specifically Scrum. I'm sure the people who designed their development process had the best intentions. However, one of the more important tenets of agile software development is that you have to get your code into the hands of testers, and customers, as soon as possible. When it can easily take a week or more just to get new code to the test team, you're losing many of the benefits of agile development processes.

Don't get me wrong, shift-left and agile processes can work together quite nicely. But they can also work against each other if you're not careful!

Does anyone else have any shift-left horror stories to share?

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