Having trouble understanding why James Bach and I think it’s important to distinguish between checking and testing? Consider this: a pile of leaves is not a tree. Leaves are important parts of trees, but there’s a lot more to a tree than just its leaves. The leaves owe their existence to being part of a larger system of the tree. Nature makes sure that leaves drop off and are replaced periodically, especially in environments that undergo significant changes from time to time. And if you asked someone to describe his tree, you’d probably—and properly—think him strange if he pointed to a pile of leaves and said, “this is my tree”.