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Today I had a twittersation about build servers, and how closely they should match the development and production environments. Damian’s position was that the build server should match the development environment, while I held that the build environment should be as close to production as possible. Martin Fowler’s Continuous Integration article says:

Test in a Clone of the Production Environment

The point of testing is to flush out, under controlled conditions, any problem that the system will have in production. A significant part of this is the environment within which the production system will run. If you test in a different environment, every difference results in a risk that what happens under test won't happen in production.

As a result you want to set up your test environment to be as exact a mimic of your production environment as possible.

I can provide an example of why this is a good idea. I am currently working on a project that is using Asp.Net MVC 2, which is installed on developer’s machines as a standalone MSI. The same article I mentioned before also says, “everything you need to do a build should be in there [repository] including: test scripts, properties files, database schema, install scripts, and third party libraries”. Being fallible, I made a mistake and failed to include one of the required MVC DLLs in the source repository. Because the build environment matched production we quickly detected the error because the build broke. If the build server was similar to the development environments then it would have had the required DLL in the GAC and the bug would have gone undetected.

Here are the things that I consider to be important for a build environment:

  1. The build server should, as close as possible, match the production environment
  2. The build server should be fast. Rapid feedback is important
  3. The same build that runs on the build server should also be runnable on the developer’s machines
  4. When a build fails, everyone should know
Posted on Thursday, November 19, 2009 5:32 AM | Back to top

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