Sometimes there is a need to have a dependencies for tests (examples, benchmarks) only. Such dependencies are added to Cargo.toml
in [dev-dependencies]
section. These dependencies are not propagated to other packages which depend on this package.
One such example is using a crate that extends standard assert!
macros.
File Cargo.toml
:
# standard crate data is left out [dev-dependencies] pretty_assertions = "0.4.0"
File src/lib.rs
:
// externing crate for test-only use #[cfg(test)] #[macro_use] extern crate pretty_assertions; pub fn add(a: i32, b: i32) -> i32 { a + b } #[cfg(test)] mod tests { use super::*; #[test] fn test_add() { assert_eq!(add(2, 3), 5); } }
Cargo docs on specifying dependencies.