The “test automation pyramid” (for examples, see here, here, and here) is a popular idea, but I see serious problems with it. I suggest in this article an alternative way of thinking that preserves what’s useful about the pyramid, while minimizing those problems:
Good analogies afford deep reasoning.
The original pyramid (really a triangle) was a context-free geometric analogy. It was essentially saying: “Just as a triangle has more area in its lower part than its upper part, so you should make more automated tests on lower levels than higher levels.” This is not an argument; this is not reasoning. Nothing in the nature of a triangle tells us how it relates to technology problems. It’s simply a shape that matches an assertion that the authors wanted to make. It’s semiotics with weak semantics.