I said this below but I like to distinguish technical debt as having metaphorical "interest" - specifically, it becomes more expensive to pay back the longer yo

I said this below but I like to distinguish technical debt as having metaphorical "interest" - specifically, it becomes more expensive to pay back the longer you leave it, the ball of debt grows over time. It's stuff that gets baked into a product, and then is difficult (or impossible) to un-bake, and gets more difficult the more the product grows around it. Aside from the initial increase in cost when you forget how the original code worked, tests are no more expensive to write in a year as they are today. Not significantly, at least. So I'd just class them as incomplete product - the effects are negative and can be expensive, but it doesn't dig you into a hole.