Macro expect_none 

macro_rules! expect_none {
    ( $option:expr ) => { ... };
}

Expects that the given Option is None; otherwise returns early.

Examples

fn passing_test() -> Result<()> {
    expect_none!(None::<()>);
    Ok(())
}

fn failing_test() -> Result<()>{
    expect_none!(Some(()));  // returns early
    Ok(())  // won't be reached
}

failing_test() will return early after calling expect_none!. The Err will be wrapped in a descriptive error message such as:

[my/file.rs:12] “expect_none!(option)” Expected None, got Some: [ contents ]“
[ … wrapped Err details …]