Fair point - I built Topaz, so yes, there's a conflict of interest. The argument about mock-vs-inject stands independently though: any proxy that sits between the SDK and a real endpoint would do the same thing. Topaz happens to be what I built to solve this for Azure locally.
Updated the title - the original was too generic for what the post actually covers. It's about Topaz, an OSS local Azure emulator I'm building.