Macro assert_ok 

macro_rules! assert_ok {
    ( $x:expr ) => { ... };
}

Assert that a Result is Ok

If the provided expresion evaulates to Ok, then the macro returns the value contained within the Ok. If the Result is an Err then the macro will panic with a message that includes the expression and the error.

This function was vendored from: https://docs.rs/assert_ok/1.0.2/assert_ok/