• Add test-case to your project Cargo.toml:

test-case = "*"

• Import test_case to the scope you are using it in:

use test_case::test_case;

Rust introduced it's own test_case to the stdlib. Due to that we must either use fully qualified path test_case::test_case or import test_case macro to the scope.

• Add test cases to your function

#[test_case(input => output_matcher ; "optional comment")]
fn testing_function(input: Type) -> ResultType {
    body!()
}

Test case syntax can be found here