Quality assurance teams, when utilizing a waterfall V-Model structure of delivery, worked in silos that retrospectively tested development changes once they were completed by a development team.
This led to quality assurance teams having to react to every development change, as it was an impossible task having to write tests for a feature they had not yet seen, or understand how it fully operated. Situations would often arise where developers without warning would commit features into source control management systems and then quality assurance teams would have to react to them:

This method of working provided lots of challenges such as:
Developers changing user interfaces, so the quality assurance team's automated tests broke as test engineers were not aware of the user interface changes
Test engineers not understanding new features meaning appropriate tests weren't written to test functionality properly
Developers having to spend lots of time explaining how...