rust-testing

Use #[tokio::test] to spin up a runtime per test, with tokio's macros and rt-multi-thread features enabled as dev-dependencies. For timeout tests, add the test-util feature and use #[tokio::test(start_paused = true)] so paused time auto-advances without real waiting.

proptest asserts invariants over generated structured inputs and shrinks failures to minimal counterexamples. cargo-fuzz throws adversarial bytes at parsers and unsafe code to find panics and memory errors, requiring the nightly toolchain and libFuzzer.

Use cargo llvm-cov for source-based LLVM coverage, optionally combined with cargo nextest via cargo llvm-cov nextest. Add --fail-under-lines 80 to gate CI, and export lcov.info for uploaders or cargo-crap risk analysis.

Use mockall's #[automock] only at true boundaries like network, clock, or payment gateways where running the real dependency is impractical. Prefer a real or in-memory implementation when feasible, since over-mocking tests your mocks instead of your code.

No, cargo nextest does not run doc tests. Run cargo test --doc separately alongside nextest, for example in a distinct CI step after the main nextest coverage run.

Use cargo-mutants for mutation testing: it makes small edits like flipping operators or deleting function bodies, then reruns the suite. Surviving mutants reveal assertion gaps; scope runs with --in-diff or -f since it rebuilds per mutant.