How to call test helper function from within integration tests?

I'm trying to figure out how to best organize my tests in Rust, and I'm running into the following problem. I have a test utility (test_util) that I define in a module and I would like to be able to use it from my unit tests as well as from my integration tests.

Definition of test_util in src/lib.rs:

#[cfg(test)]
pub mod test_util {
    pub fn test_helper() {}
}

I can access my helper function from my unit tests in another module, src/some_module.rs:

#[cfg(test)]
pub mod test {
    use crate::test_util::test_helper;

    #[test]
    fn test_test_helper() {
        test_helper();
    }
}

However, when I try to use the utility from my integration test, as in tests/integration_test.rs:

use my_project::test_util::test_helper;

#[test]
fn integration_test_test_helper() {
    test_helper();
}

I get the following compiler message:

8 | use my_project::test_util::test_helper;
  |                 ^^^^^^^^^ could not find `test_util` in `my_project`

Is there a good reason why it is not allowed to access test code from the project from within an integration test belonging to that same project? I get it that integration tests can only access the public parts of the code, but I think it would make sense to also allow access to the public parts of the unit test code. What would be a work around for this?