Regression Testing and Deployment Strategy

Question

I'd like some advice on a deployment strategy. If a development team creates an extensive framework, and many (20-30) applications consume it, and the business would like application updates at least every 30 days, what is the best deployment strategy?

The reason I ask is that there seems to be a lot of waste (and risk) in using an agile approach of deploying changes monthly, if 90% of the applications don't change. What I mean by this is that the framework can change during the month, and so can a few applications. Because the framework changed, all applications should be regression-tested. If, say, 10 of the applications don't change at all during the year, then those 10 applications are regression-tested EVERY MONTH, when they didn't have any feature changes or hot fixes. They had to be tested simply because the business is rolling updates every month.

And the risk that is involved... if a mission-critical application is deployed, that takes a few weeks, and multiple departments, to test, is it realistic to expect to have to constantly regression-test this application?

One option is to make any framework updates backward-compatible. While this would mean that applications don't need to change their code, they would still need to be tested because the underlying framework changed. And the risk involved is great; a constantly changing framework (and deploying this framework) means the mission-critical app can never just enjoy the same code base for a long time.

These applications share the same database, hence the need for the constant testing. I'm aware of TDD and automated tests, but that doesn't exist at the moment.

Any advice?

Answer 1

Here are some tips I can think of: 1. break the framework into independent parts, so that changing one part requires only running a small portion of test cases. 2. Employ a test case prioritizaion technique. That is, you only rerun a small portion of the test pools of the applications selected by some strategy. Additional branch and ART have better performance than others usually. They require to know the branch coverage information of each test case. 3. Update the framework less frequently. If an application doesn't need change, it means its ok not to change it. So I guess its ok for these applications to use the old version of the framework. You can update the framework for these applications say every 3 months.

Answer 2

The idea behind a framework is that it's supposed to be the "slow moving code". You shouldn't be changing the framework as frequently as the applications it supports. Try getting the framework on a slower development cycle: perhaps a release no more often than every three or six months.

My guess is that you're still working out some of the architectural decisions in this framework. If you think the framework changes really need to be that dynamic, find out what parts of the framework are being changed so often, and try to refactor those out to the applications that need them.

Agile doesn't have to mean unlimited changes to everything. Your architect could place boundaries on what constitutes the framework, and keep people from tweaking it so readily for what are likely application shortcuts. It may take a few iterations to get it settled down, but after that it should be more stable.

Answer 3

Regression testing is a way of life. You will need to regression test every application before it is released. However, since time and money are not usually infinite, you should focus your testing on the areas with the most changes. A quick and dirty way to identify these areas is to count the lines of code changed in a given business area; say "accounting" or "user management". Those should get the most testing first along with any areas that you have identified as “mission critical”.

Now I know that lines of code changed is not necessarily the best way to measure change. If you have well defined change requests, it is actually better to evaluate these hot spots by looking at the number and complexity of the change requests. But not everyone has that luxury.

When you are talking about making a change to the framework, you probably don't need to test all the code that uses it. If you're talking about a change to something like the DAL, that would basically amount to everything anyway. You just need to test a large enough sample of the code to be reasonably comfortable that the change is solid. Again, start with the "mission critical" areas and the area most heavily affected.

I find it helpful to divide the project into 3 distinct code streams; Development, QA, and Production. Development is open to all changes, QA is feature locked, and Production is code locked (well, as locked as it gets anyway). If you are releasing to production on a monthly cycle, you probably want to branch a QA build from the Development code at least 1 month before the release. Then you spend that month acceptance testing the new changes and regression testing everything else that you can. You'll probably have to complete testing the changes about a week before the release so that the app can be staged and you can dry run the installation a few times. You won't get to regression test everything, so have a strategy ready for releasing patches to Production. Don't forget to merge those patches back into the QA and Development code streams too.

Automating the regression tests would be a really great thing; theoretically. In practice, you end-up spending more time updating the testing code then you would spend running the test scripts manually. Besides, you can hire two or three testing monkeys for the price of one really good test script developer. Sad but true.

Answer 4

I wouldn't call it an Agile approach unless you have (unit) test coverage. One of the key tenets of Agile is that you have robust unit tests that provide a safety net for frequent refactoring and new feature development. There is a lot of risk in your scenario. Deploying twenty to thirty applications a month when 1) most of them don't add any new business value to their users; and 2) there are no tests in place would not qualify as a good idea in my book. And I'm a strong believer in Agile. But you can't pick and choose only the parts of it that are convenient.

If the business application has not changed, I wouldn't release it just to compile in a new framework. Imagine every .NET application needing to be re-released every time the framework changed. Reading into your question, I wonder if the common database is driving the need for this. If your framework is isolating the schema and you're finding you need to rebuild apps whenever the schema changes, then you need to tackle that problem first. Check out Refactoring Databases, by Scott Ambler for some tips.

As another aside, there's a big difference between integration test and unit tests. Your regression tests are integration tests. It's very difficult to automate at that level. I think the breakthroughs that are happening in testing are all about writing highly testable code that makes unit testing more and more of the code base possible.