Continuous Delivery: Reliable Software Releases through Build, Test, and Deployment Automation

by David Farley

Once you know the cycle time for your application, you can work out how best to reduce it. You can use the Theory of Constraints to do this by applying the following process. 1. Identify the limiting constraint on your system. This is the part of your build, test, deploy, and release process that is the bottleneck. To pick an example at random, perhaps it’s the manual testing process. 2. Exploit the constraint. This means ensuring that you should maximize the throughput of that part of the process. In our example (manual testing), you would make sure that there is always a buffer of stories waiting to be manually tested, and ensure that the resources involved in manual testing don’t get used for anything else. 3. Subordinate all other processes to the constraint. This implies that other resources will not work at 100%—for example, if your developers work developing stories at full capacity, the backlog of stories waiting to be tested would keep on growing. Instead, have your developers work just hard enough to keep the backlog constant and spend the rest of their time writing automated tests to catch bugs so that less time needs to be spent testing manually. 4. Elevate the constraint. If your cycle time is still too long (in other words, steps 2 and 3 haven’t helped enough), you need to increase the resources available—hire more testers, or perhaps invest more effort in automated testing. 5. Rinse and repeat. Find the next constraint on your system and go back to step 1.

Using lessons from the book "The Goal", here's how to reduce cycle time og development