I wrote to the post of Andrea (a dev from the Copilot team) about their 800K LoC: 128 PRs, shipped incrementally. Existing end-to-end tests ran against the new code at every step.

Total: ~1,301,378 lines of Rust.

Production: 832,378 Unit tests: ~469,000 Combined: ~1.30 million lines

On top of the 832K LoC are mostly tests she answered:

> Yeap, 832,378 lines of production Rust. the +800K number is production only; unit tests are another +469K on top.

https://x.com/acolombiadev/status/2100660224298193081?s=20

> Half of the 832K LoC are mostly tests she answered:

No? That quote is clearly saying the opposite of your summary.