XBreed
The Scrum and XP combination that XBreed formalizes is in fact one of the most common among mature agile teams, whether or not the name "XBreed" is applied to it. Scrum provides the management structure (roles, events, artifacts); XP contributes the technical practices that make that management sustainable over the long term: TDD, pair programming, refactoring, and continuous integration. As a formal methodology, XBreed has not had any particular relevance or adoption in the industry. Its current value is mainly historical: it shows that, from the early years of agility, there was an awareness that Scrum alone was not enough and that it needed to be complemented with solid engineering practices.
Common mistake
Assuming that Scrum includes technical practices. Scrum does not prescribe any engineering practice: it says nothing about how to write code, how to test, or how to manage technical debt. XBreed, as a combination of Scrum and XP, was a deliberate response to that limitation. Teams that adopt Scrum without agile technical practices (TDD, continuous integration, refactoring) tend to accumulate technical debt that sooner or later slows down development.
See also
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