mutagen VS cargo-mutants

There are two testing techniques you didn't mention: Snapshot tests (which are greatly simplified using the insta crate and mutation testing (which can be done on nightly with my mutagen crate.

How does this compare to mutagen?

Do you mean as part of build.rs? Yes, that's certainly doable, and has been done in the past. You can use env!("OUT_DIR") for that. Examples you may want to refer to include my mutagen crate and criterion.

Would be great if this could include mutation testing.

I wrote a good number of macros though, both macro_rules! and various proc_macros. The latest iteration of overflower has both, for example. mutagen is a mutation testing tool built as a proc macro, and it's helper library has a bunch of macros, too. compact_arena uses macros to tie unique lifetime tags to arenas.

Also there are far more mutation testing frameworks. I maintain the rust-based mutagen one. There are also LLVM-based ones (etc. mull) that can cover multiple languages (but may yield mutations not expressible in your preferred one).

Cargo (and Rust) makes it so easy to write test cases that you should really use it to find these kinds of bugs. And there are other good test crates available: mutagen, quickcheck, etc.

I had a student completely reachitecture my mutagen tool, and saw some working on various clippy contributions.

Hi Rusty!

For a later hack in the same vein, check out https://github.com/sourcefrog/cargo-mutants

cargo-mutants got a couple of releases over the weekend, fixing some environment-triggered bugs on Windows and Linux ecryptfs, and adding a better overall progress indicator (demo: https://asciinema.org/a/481375). It is getting better at avoiding uninteresting or pointless mutations, although there's a lot more to do there, and at printing function name paths well.

While working on Conserve and cargo-mutants I felt that existing Rust progress-bar libraries like Indicatif didn't give me enough control of how the bar was drawn, or at least I was working around them to insert my own text. For example, I wanted to draw several counters into a single line, and it seems like the only way to do that is to just push in a text string.

Continuing with some fast-follow enhancements in cargo-mutants in response to user feedback: for example doctests are typically slow and in some trees not important for coverage, so you can now skip them.

I got cargo-mutants to a state where I felt I could announce it and ask for public feedback.