Test-driven development is one of the corner stones of Agile development, providing quick feedback about mistakes in code and freeing developers to refactor safe in the knowledge that any errors they introduce will be caught by the tests. There have been several test harnesses developed for XSLT, of which XSpec is one of the latest. XSpec draws inspiration from the behaviour-driven development framework for Ruby, called RSpec, and focuses on helping developers express the desired behaviour of their XSLT code. This talk will discuss the XSpec language, its implementation in XSLT 2.0, and experience with using XSpec on complex, large-scale projects.