unit-testingrustconditional-compilation

How to make a test for a function defined under some configuration?

How to make a unit test for a function defined some configuration like what follows

struct I32Add;
impl I32Add{
    #[cfg(unstable)]
    fn add(x:i32, y:i32) -> i32{x+y}
}

#[test]
fn add_test(){
    assert_eq!(I32Add::add(1,2),3)
}

Of course, the test doesn't work. how to make it work?

Solution

  • You can add #[cfg(unstable)] to your test just as you've done for your function. So the test is only compiled if that function is compiled:

    #[cfg(unstable)]
#[test]
fn add_test() {
    assert_eq!(I32Add::add(1, 2), 3)
}

    To get your function and the test to compile and run, you have to enable the unstable config option:

    RUSTFLAGS="--cfg unstable" cargo test

    However, I would recommended that you use a cargo feature instead of a config option for conditionally enabling portions of your code-base.

    struct I32Add;
impl I32Add{
    #[cfg(feature = "unstable")]
    fn add(x:i32, y:i32) -> i32{x+y}
}

#[cfg(feature = "unstable")]
#[test]
fn add_test(){
    assert_eq!(I32Add::add(1,2),3)
}

    with this in your cargo.toml:

    [features]
unstable = []

    And then run it like:

    cargo test --features=unstable

    See: