The Timeboxed Iteration practice defines that all iterations should have a fixed time duration. Thus, an iteration should not be extended or shortened to fit planned or unplanned features. The Absence of Timeboxed Iteration smell is detected when an iteration is shorter or longer than the predefined duration. The presence of this smell may indicate the timeboxed iteration practice has not been applied properly.
Agile Methods: The Timeboxed Iteration practice is mentioned by four methods: Scrum, DSDM, ADS and OpenUp. Scrum method defines that an iteration (called sprint in Scrum) should be timeboxed. In DSDM, the Deliver On Time principle states that delivering a solution on time is a very desirable outcome for a project and is quite often the single most important success factor. In order to achieve this principle, DSDM teams should need to timebox work. ADS method argues that ambiguity in complex software development can be alleviated by fixing tangible deadlines on a regular basis. The Iterative Development practice in OpenUp defines that do not extend an iteration in order to finish work.
Industry Perspective: Regarding the survey, there was no unanimity among the participants. Some participants said timeboxing should be rigidly followed. Other subjects said that timeboxing is desired, but not applied as a rigid rule. Changes in iteration duration are indeed a common practice. For these participants, it is preferable to extend an iteration in order to include important features than achieve timeboxing with less features.
Identification Strategy: Timeboxing could be verified assessing if there was any variation in the iteration duration after it has been planned.
Parameters: A Tolerance Of Change parameter (absolute or percentage value) could be used to indicate the maximum tolerated variation. For example, a 5% tolerance means that an iteration could have their duration shortened or extended by 5% of its baseline duration.