How to include function in documentation test example? - testing

Question

I am trying to make a simple documentation example but it doesn't compile. I tried:
/// Given an axis in 3D returns the indices of the 3 basis axis in the order such
/// that the first index represents forward (the input) the next the side and the final
/// the up. i.e. it computes the even permutation of basis index that creates the
/// rotation that aligns the basis with the selected axis.
///
/// # Arguments
///
/// * index an index from 0-2 selecting the forward axis.
///
/// # Examples
///
/// ```
/// use crate::axis_index_to_basis_indices;
/// let x_index = 0;
/// let y_index = 1;
/// let z_index = 2;
/// let (forward, side, up) = axis_index_to_basis_indices(x_index);
/// assert!(forward == x_index);
/// assert!(side == y_index);
/// assert!(up == z_index);
///
/// let (forward, side, up) = axis_index_to_basis_indices(z_index);
/// assert!(forward == z_index);
/// assert!(side == x_index);
/// assert!(up == y_index);
/// ```
fn axis_index_to_basis_indices(index: i32) -> (i32, i32, i32)
{
match index
{
0 => (0, 1, 2),
1 => (1, 2, 0),
2 => (2, 0, 1),
_ => panic!(),
}
}
Which gives:
error[E0432]: unresolved import `crate::axis_index_to_basis_indices`
--> dual_contouring.rs:107:5
|
3 | use crate::axis_index_to_basis_indices;
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ no `axis_index_to_basis_indices` in the root
error: aborting due to previous error
For more information about this error, try `rustc --explain E0432`.
Couldn't compile the test.
failures:
dual_contouring.rs - axis_index_to_basis_indices (line 106)
test result: FAILED. 0 passed; 1 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.02s
error: doctest failed, to rerun pass `--doc`
The official docs are incomplete in this regard. Reading them one would assume the include statement should be use doc::name_of_crate but that also doesn't work.