feat: add tests

__std/misc/src/bin/dynamic_bind_test.rs

@@ -0,0 +1,20 @@
+trait Say {
+    fn say(&self);
+}
+
+struct Dog {}
+
+impl Say for Dog {
+    fn say(&self) {
+        println!("Wangwang!");
+    }
+}
+
+fn do_say(s: Box<dyn Say>) {
+    s.say();
+}
+
+fn main() {
+    let dog = Dog {};
+    do_say(Box::new(dog));
+}