Crispin stated that in order to deal with defects, one had to lower the bar for defects. She used a limbo analogy for this, where the bar gets lowered and lowered. She presented form her team which had strived for zero bugs for several years, and when and how to log defects and track them.
On the traditional view on defect tracking, these systems are used for metrics and to help the team to know what to fix. Customers also may want to get an insight into the defect tracking system in order to understand which errors they might have to deal with when buying the software.
In the Agile view defect tracking is a waste in the Lean sense. Striving for zero defects is the goal to try to achieve there. Instead of filing bug in the tracking system, Agile teams work on creating an automated test first, which reproduces the problem in the system, and then to have any regressions being dealt with by the continuous integration framework.
On the advantages of using a tool to log bugs Crispin mentioned that the tool might provide the metrics necessary on more traditional teams. Also, the customer can get a hindsight of the quality of the system, and managers may use it to control the project.
On the downsides of a defect tracking system, it takes usually more time to file a bug than to write an automated test which exposes the problem. On an Agile team you can use color-coded story cards to track defects instead of having a second backlog from which work is taken by the team. Color-coded bug cards reveal problems in the process as well.
Crispin presented the approach her team takes in order to deal with defects. For unit level bugs they most of the time write an automated unit test instead of filing a bug, and fixing the problem immediately. The same holds for functional regressions, which then yields in a functional tests on the story-level. Some bugs they file for later, putting them effectively into their product backlog as a new story, which gets estimated and prioritized together with the rest. In addition Crispin mentioned that her team tries to avoid to put anything into the defect tracking system which they know they are not going to fix any way.
Finally, Crispin mentioned that getting a team to zero defects takes years, especially when dealing with legacy and fragile code. Her team achieved this, but it’s a journey worthwhile to take on.