feat: update tests

__std/misc/src/bin/chain_test.rs

@@ -0,0 +1,30 @@
+#[derive(Debug)]
+struct Node {
+    value: i32,
+    next: Option<Box<Node>>,
+}
+
+fn build_chain() -> Option<Box<Node>> {
+    let mut p = None;
+    for i in 0..3 {
+        p = Some(Box::new(Node {
+            value: i,
+            next: p,
+        }));
+    }
+    p
+}
+
+fn print_chain(mut p: &Option<Box<Node>>) {
+    let mut values = vec![];
+    while let Some(node) = p {
+        values.push(node.value.to_string());
+        p = &node.next;
+    }
+    println!("{}", values.join(" -> "))
+}
+
+fn main() {
+    let p = build_chain();
+    print_chain(&p);
+}