How to define test-only dependencies?

I have a Rust library that implements a lint plugin. I want to include compiletest, but not require it outside of testing. What is the correct way to specify that the dependency is for testing only?

Use dev-dependencies. From the Cargo docs:

You can add a [dev-dependencies] section to your Cargo.toml whose format is equivalent to [dependencies]:
[dev-dependencies]
tempdir = "0.3"


Dev-dependencies are not used when compiling a package for building,
but are used for compiling tests, examples, and benchmarks.

When possible, you should also use Cargo's resolver version 2 to better handle complicated dev-dependency cases.

Stack Overflow Q#29857002, score: 144