In the last few posts I have discussed some of, what I consider to be, the most valuable Agile methods for development. The list is pretty long, so breaking the list up allows me to define each practice and include the individual benefit of each Agile method. This post defines some hot terms right now- continuous integration, multistage continuous integration, and story points. Enjoy!
Agile Method: Continuous Integration
How frequently have you merged your code with changes from the mainline, only to find that the result doesn’t build, or it builds but it doesn’t work? Monthly? Weekly? Daily? Hourly? Or worse, how often have you made changes that broke the build, requiring you to quickly correct the problem while getting flames from your team members?
A practice that has emerged to address the problems of integration is called Continuous Integration. The basic idea is that if integrating changes together and getting build and test results on a regular basis is a good idea, integrating and getting build and test results on every change is even better.
With Continuous Integration, all work from all teams is integrated into a single codeline as frequently as possible. Every check-in automatically triggers a build and usually a subsequent run of the test suite. This provides instant feedback about problems to all interested parties and helps to keep the code base free of build and test failures. It also reduces the integration headaches just prior to release.
Agile Method: Multi-stage Continuous Integration
Integration is tough enough when you are just integrating your work with the work of other folks in your small team, or the whole effort is being done by a small team, but when you are part of a large team there is also something called “Big-Bang” integration. That’s the integration of the work that multiple teams have been working on for long periods of time. In a typical project, this integration is done in a phase toward the end of the project. During integration, many problems are discovered for the first time which leads to delays and/or changes in scope.
The real question is, what is a good way to structure this integration so that it will scale smoothly as you add more people to the equation? A good starting place is to look around for a pattern to follow. What are some similar situations? I have found that everything your organization needs to do in order to produce the best possible development organization can be entirely derived from the patterns and practices at the individual level. This approach makes it much easier to understand and much more likely that it will be successfully followed.
As individuals we work in transient isolation to reduce the impact of work in progress on each other. Organizations isolate WIP by using only official versions of 3pty sources and by producing official releases for customers.
Multi-stage continuous integration (MSCI) scales CI to large distributed environments by isolating work in progress at the team level. Changes move from individual to team to mainline as fast as CI allows, but stop on failure. MSCI is particularly important in a distributed environment where fixes to problems exposed by CI can be delayed by a full day
Agile Method: Using Story Points For Estimation, Instead of Units of Time
In my experience, the best unit to use for estimates is story points. Two different people with two different skill sets or levels of ability in an area may take different amounts of time to perform a particular task. Estimating in hours mixes together the scope of the work that needs to be done with the speed at which a particular individual can do that work.
On the other hand, story points are a relative measure of the scope of a user story. Story points separates out the “what” from the “who.” For instance, if you have one individual that is stronger with .Net than with Java, they will estimate a Java story as taking more hours than somebody that is stronger with Java. But they will probably both agree that something that is twice as easy to implement will take half as long to do.
To use story points, you need to create a relative scale of scope. A simple approach is to find a simple and straightforward story that you use to represent a single story point. Then think of stories that are 2, 3, 5, and 8 times larger in scope. You should have a couple of examples for each story point value to take into account that some stories have more test than coding, more documentation than test, etc.
Story points are primarily used for planning, not for implementation. Story points are used to help determine the contents of release by calculating a velocity.
Next up: Backlog, velocity, planning poker and burnup charts.
