This paper reported the experience of attempting to use FIT as the single source of behavioral requirements for the user stories, hoping to reduce duplication and ambiguity between multiple documents. The first challenge faced was that using FIT made collaboration more difficult between team members and stakeholders. This was due to additional time needed for the stakeholders to learn and understand the FIT syntax, often using their time with team members to work on getting the FIT documents syntactically correct. The teams found that using FIT allowed for greater confidence refactoring existing code, as the tests should theoretically catch broken functionality.
Using FIT also allowed team members to identify new domain concepts, such as being able to break down a single complex business rule into smaller individual rules. Another challenge addressed was ensuring that the FIT documents were kept up-to-date, ensuring the requirements were not going stale. Along the same lines, additional organization was introduced to maintain the growing volume of documents. Additional consideration also needed to be made for personnel organization, as it was found that the best results came from direct collaboration on FIT documents between developers and business stakeholders. It was also found that after the team size increased rapidly (from 6 to 24 developers), the living FIT documents allowed for a consistent and correct place for the new developers to go to for information.