Cargo looks for integration tests in tests directory next to src.
File src/lib.rs:
// Define this in a crate called `adder`.
pub fn add(a: i32, b: i32) -> i32 {
a + b
}
File with test: tests/integration_test.rs:
#[test]
fn test_add() {
assert_eq!(adder::add(3, 2), 5);
}
