Add clone_multiple_into_external ref preservation test

rbx_dom_weak/src/dom.rs

@@ -555,6 +555,45 @@ mod test {
         insta::assert_yaml_snapshot!(viewer.view(&other_dom));
     }
 
+    #[test]
+    fn clone_multiple_into_external() {
+        let dom = {
+            let mut child1 = InstanceBuilder::new("Part").with_name("Child1");
+            let mut child2 = InstanceBuilder::new("Part").with_name("Child2");
+
+            child1 = child1.with_property("RefProp", child2.referent);
+            child2 = child2.with_property("RefProp", child1.referent);
+
+            WeakDom::new(
+                InstanceBuilder::new("Folder")
+                    .with_name("Root")
+                    .with_children([child1, child2]),
+            )
+        };
+
+        let mut other_dom = WeakDom::new(InstanceBuilder::new("DataModel"));
+        let cloned = dom.clone_multiple_into_external(&dom.root().children(), &mut other_dom);
+
+        assert!(
+            other_dom.get_by_ref(cloned[0]).unwrap().parent.is_none(),
+            "parent of cloned subtree root should be none directly after a clone"
+        );
+
+        assert!(
+            other_dom.get_by_ref(cloned[1]).unwrap().parent.is_none(),
+            "parent of cloned subtree root should be none directly after a clone"
+        );
+
+        other_dom.transfer_within(cloned[0], other_dom.root_ref);
+        other_dom.transfer_within(cloned[1], other_dom.root_ref);
+
+        let mut viewer = DomViewer::new();
+
+        // This snapshot should contain Child1 and Child2, with Child1's and Child2's ref
+        // properties rewritten to point to the newly cloned instances
+        insta::assert_yaml_snapshot!(viewer.view(&other_dom));
+    }
+
     #[test]
     fn large_depth_tree() {
         // We've had issues with stack overflows when creating WeakDoms with

rbx_dom_weak/src/snapshots/rbx_dom_weak__dom__test__clone_multiple_into_external.snap

@@ -0,0 +1,22 @@
+---
+source: rbx_dom_weak/src/dom.rs
+expression: viewer.view(&other_dom)
+---
+referent: referent-0
+name: DataModel
+class: DataModel
+properties: {}
+children:
+  - referent: referent-1
+    name: Child1
+    class: Part
+    properties:
+      RefProp: referent-2
+    children: []
+  - referent: referent-2
+    name: Child2
+    class: Part
+    properties:
+      RefProp: referent-1
+    children: []
+