1️⃣ Formal verification offers full‑system guarantees that testing cannot
“To a first approximation, formal verification can guarantee some property holds for every possible run of the program, rather than just the tested ones.” — gr_norm
2️⃣ Real‑world systems (e.g., GUIs, massive platforms) make specification extremely hard
“Anything with a GUI seems really daunting to specify. And then later you need to update specs to match GUI if you make any changes…” — IsTom
“Real‑world systems are too messy to be specified.” — bananaflag
3️⃣ The model‑code gap: a verified spec must still be linked to the actual implementation
“Now I have two artifacts: TLA+ specification → proved; Rust implementation → runtime… What I actually need is: Rust_Program → Safety.” — sp1982