Tracking

Tracking and managing an XP project is a matter of recording the results of each iteration and then using those results to predict what will happen in the next iterations. Consider, for example, Figure 3-1. This graph is called a velocity chart. We would normally find it on the wall of the project war room.

Figure 3-1. Velocity chart

This chart shows how many story points were completedpassed their automated acceptance testsat the end of each week. Although there is some variation between the weeks, the data clearly shows that this team is completing around 42 story points per week.

Consider also the graph in Figure 3-2. This so-called burn-down chart shows, on a week-by-week basis, how many points remain to be completed for the next major milestone or release. The slope of this chart is a reasonable predictor of the end date.

Figure 3-2. Burn-down chart

Note that the difference between the bars in the burn-down chart does not equal the height of the bars in the velocity chart. The reason is that new stories are being added to the project. It may also indicate that the developers have re-estimated the stories.

When these two charts are kept on the wall of the project room, anybody can look them over and tell within seconds what the status of the project is. They can tell when the next major milestone will be met and to what degree the scope and estimates are creeping. These two charts are the true bottom line for XP and all the agile methods. In the end, it's all about generating reliable management information.