Rereading my post, I see where it sounds more strawman of the "entire wall of tests." I did not mean it to be the final test suite is written first.

Instead, I intended that to be the wall that you will be passing in a given cycle. So, for a small development cycle, you add in some new tests that will be this cycle's "wall" of failing tests that you flip to passing.

And don't take this to be an indication that I think integration tests are somehow superior. They all have advantages and there is a massive cost benefit tradeoff that has to be considered at all times.

It is easy to talk in strawmen. Such that I can confidently say if you have a set of tests that always fails together, that should just be a single test. However, I do not feel that statements like that are informative, precisely because it is a judgement call masquerading as a rule.