diff --git a/test/Encoder.test.ts b/test/Encoder.test.ts
index 4be0081..761c790 100644
--- a/test/Encoder.test.ts
+++ b/test/Encoder.test.ts
@@ -1,7 +1,7 @@
 import * as assert from "assert";
-import { MapSchema, Schema, type, ArraySchema, defineTypes, Reflection, Encoder, $changes } from "../src";
+import { MapSchema, Schema, type, ArraySchema, defineTypes, Reflection, Encoder, $changes, entity } from "../src";
 
-import { State, Player, getCallbacks, assertDeepStrictEqualEncodeAll, createInstanceFromReflection } from "./Schema";
+import { State, Player, getCallbacks, assertDeepStrictEqualEncodeAll, createInstanceFromReflection, getEncoder, getDecoder } from "./Schema";
 
 describe("Encoder", () => {
     const bufferSize = Encoder.BUFFER_SIZE;
@@ -25,4 +25,126 @@ describe("Encoder", () => {
         decodedState.decode(state.encode());
     });
 
+    Encoder.BUFFER_SIZE = 16 * 1024;
+
+    describe("dynamic schema operations", () => {
+        /**
+         * Helper that encodes the state, decodes into a fresh reflected instance,
+         * and asserts deep equality + refId/refCount match between encoder & decoder.
+         */
+        function encodeDecodeAndAssert<S extends Schema>(state: S) {
+            const encoder = getEncoder(state);
+            const bytes = state.encode();
+            const decodedState = createInstanceFromReflection(state);
+            const decoder = getDecoder(decodedState);
+            decodedState.decode(bytes);
+            assertDeepStrictEqualEncodeAll(state);
+            // Ensure refId counts match between encoder & decoder
+            for (const refId in encoder.root.refCount) {
+                assert.strictEqual(
+                    encoder.root.refCount[refId],
+                    decoder.root.refCounts[refId] ?? 0,
+                    `refCount mismatch for refId=${refId}`
+                );
+            }
+        }
+
+        it("should handle moving shared instances between array <-> map <-> field", () => {
+            class Item extends Schema {
+                @type("string") id: string = Math.random().toString(36).slice(2);
+            }
+            class Container extends Schema {
+                @type([Item]) list = new ArraySchema<Item>();
+                @type({ map: Item }) bag = new MapSchema<Item>();
+                @type(Item) equipped: Item;
+            }
+
+            const state = new Container();
+
+            // create two shared items
+            const sword = new Item();
+            const shield = new Item();
+
+            // initial placement
+            state.list.push(sword, shield);
+            encodeDecodeAndAssert(state);
+
+            // move "sword" from array to map key "sword"
+            state.bag.set("sword", sword);
+            state.list.splice(state.list.indexOf(sword), 1);
+            encodeDecodeAndAssert(state);
+
+            // equip the sword (shared reference now field & map)
+            state.equipped = sword;
+            encodeDecodeAndAssert(state);
+
+            // unequip and move back to array
+            state.equipped = undefined;
+            state.list.push(sword);
+            state.bag.delete("sword");
+            encodeDecodeAndAssert(state);
+        });
+
+        it("should replace instances multiple times in nested structures", () => {
+            class Child extends Schema {
+                @type("number") value: number = 0;
+            }
+            class Parent extends Schema {
+                @type(Child) a: Child;
+                @type(Child) b: Child;
+            }
+
+            const state = new Parent();
+            const c1 = new Child().assign({ value: 1 });
+            const c2 = new Child().assign({ value: 2 });
+            const c3 = new Child().assign({ value: 3 });
+
+            state.a = c1;
+            state.b = c1; // shared initially
+            encodeDecodeAndAssert(state);
+
+            // replace a with new instance
+            state.a = c2;
+            encodeDecodeAndAssert(state);
+
+            // replace b with another new instance
+            state.b = c3;
+            encodeDecodeAndAssert(state);
+
+            // finally point both to same again
+            state.a = state.b;
+            encodeDecodeAndAssert(state);
+        });
+
+        it("should survive clear & repopulate on ArraySchema with shared children", () => {
+            class Node extends Schema {
+                @type("string") id: string = Math.random().toString(36).substring(2);
+            }
+            class Graph extends Schema {
+                @type([Node]) nodes = new ArraySchema<Node>();
+                @type({ map: Node }) lookup = new MapSchema<Node>();
+            }
+
+            const state = new Graph();
+            // add 5 nodes, share references between array & map
+            for (let i = 0; i < 5; i++) {
+                const n = new Node();
+                state.nodes.push(n);
+                state.lookup.set(n.id, n);
+            }
+            encodeDecodeAndAssert(state);
+
+            // clear array – map still holds them
+            state.nodes.clear();
+            encodeDecodeAndAssert(state);
+
+            // repopulate array using map values (shared again)
+            state.lookup.forEach(node => state.nodes.push(node));
+            encodeDecodeAndAssert(state);
+
+            // now clear map completely
+            state.lookup.clear();
+            encodeDecodeAndAssert(state);
+        });
+    });
 });