[kccqzy]

Formal verification is often not the best tool for ensuring code correctness from an ROI perspective. Things like unit tests (including property based tests) and ensuring 100% code coverage often achieve adequate results with less effort.

[jlouis]

The key point is that most software don't need correctness to the level formal verification provides. There's a subset of software however, for which there's no substitute for a formal verification process.

[aSanchezStern]

Additionally, formal verification usability is an area of constant research, and the set of software for which it is the best ROI increases over time.

[pfdietz]

If you can specify your program (or a part of it) well enough to prove it correct, you can also use that specification for property-based testing.