A TDL (Test Description Language) is a constructed language that we use to describe, and thus specify, our requirements as tests. Or our tests as requirements, if you prefer. This is what allows testing to be a design activity. What makes a style of writing a TDL is adherence to a structuring element and a set of principles and patterns that are used to guide expression.

Current forms of TDL swirl around various BDD concepts, such as Given-When-Then. But it’s clear that just having that focus in place does nothing for you by itself because there is a lot of thought that goes into how you want to express yourself. I’ve found many testers really struggle with this but, equally, I’ve found I struggle in being able to adequately teach at what level you work at with a TDL.