>This is precisely waterfall

I'm not sure I fully agree, unless we want to define waterfall as "anything where a bit of time is spent up-front to decide how a part of the system should work" :)

For me, waterfall is where every single aspect of the project is pre-defined, and cannot be changed during development without serious pain and lots of awful bureaucracy

But in the above workflow, there isn't anything stopping us from making a loop for example on a sprint by sprint basis, and using feedback from both the tests and changing requirements to improve the design, update the APIs, change the tests, etc.

I suppose we could argue that this is "mini-waterfall" but it works in my experience :)