Function preorder_recursive

tests/test_tree_traverse.rs:85–95

()

#[test]
fn preorder_recursive() {
    for (t, expect) in preorder_test_data() {
        let mut tree: Tree<usize, usize> = TreeBuilder::build_in_level(t.as_slice());
        let r = unsafe { PreOrderVisitor::recursive(&mut tree) };
        assert_eq!(
            expect, r,
            "tree = {:?}, expect = {:?}, r = {:?}",
            t, expect, r
        );
    }
}

#[test]
fn inorder_iter() {