I find myself creating test helpers/mocks in my test modules that are marked with #[cfg(test)]. They are exported as pub and can conveniently be used throughout the crate.
These helpers are not visible from other crates nor from integration tests in particular.

Making code compiled with cfg(test) be visible outside of the scope of a crate would allow for better code reuse. Please consider adapting that behavior.

Related: rust-lang/rust#45599