diff --git a/packages/reactivity/__tests__/reactive.spec.ts b/packages/reactivity/__tests__/reactive.spec.ts
index ab798ff2c8b..a7c46451d1e 100644
--- a/packages/reactivity/__tests__/reactive.spec.ts
+++ b/packages/reactivity/__tests__/reactive.spec.ts
@@ -1,6 +1,7 @@
 import { ref, isRef } from '../src/ref'
 import { reactive, isReactive, toRaw, markRaw } from '../src/reactive'
 import { computed } from '../src/computed'
+import { effect } from '../src/effect'
 
 describe('reactivity/reactive', () => {
   test('Object', () => {
@@ -44,22 +45,59 @@ describe('reactivity/reactive', () => {
     expect(isReactive(observed.array[0])).toBe(true)
   })
 
-  test('process subtypes of collections properly', () => {
-    class CustomMap extends Map {
-      count = 0
+  test('observing subtypes of IterableCollections(Map, Set)', () => {
+    // subtypes of Map
+    class CustomMap extends Map {}
+    const cmap = reactive(new CustomMap())
 
-      set(key: any, value: any): this {
-        super.set(key, value)
-        this.count++
-        return this
-      }
-    }
+    expect(cmap instanceof Map).toBe(true)
+    expect(isReactive(cmap)).toBe(true)
+
+    cmap.set('key', {})
+    expect(isReactive(cmap.get('key'))).toBe(true)
+
+    // subtypes of Set
+    class CustomSet extends Set {}
+    const cset = reactive(new CustomSet())
+
+    expect(cset instanceof Set).toBe(true)
+    expect(isReactive(cset)).toBe(true)
+
+    let dummy
+    effect(() => (dummy = cset.has('value')))
+    expect(dummy).toBe(false)
+    cset.add('value')
+    expect(dummy).toBe(true)
+    cset.delete('value')
+    expect(dummy).toBe(false)
+  })
+
+  test('observing subtypes of WeakCollections(WeakMap, WeakSet)', () => {
+    // subtypes of WeakMap
+    class CustomMap extends WeakMap {}
+    const cmap = reactive(new CustomMap())
+
+    expect(cmap instanceof WeakMap).toBe(true)
+    expect(isReactive(cmap)).toBe(true)
+
+    const key = {}
+    cmap.set(key, {})
+    expect(isReactive(cmap.get(key))).toBe(true)
+
+    // subtypes of WeakSet
+    class CustomSet extends WeakSet {}
+    const cset = reactive(new CustomSet())
+
+    expect(cset instanceof WeakSet).toBe(true)
+    expect(isReactive(cset)).toBe(true)
 
-    const testMap = new CustomMap()
-    const observed = reactive(testMap)
-    expect(observed.count).toBe(0)
-    observed.set('test', 'value')
-    expect(observed.count).toBe(1)
+    let dummy
+    effect(() => (dummy = cset.has(key)))
+    expect(dummy).toBe(false)
+    cset.add(key)
+    expect(dummy).toBe(true)
+    cset.delete(key)
+    expect(dummy).toBe(false)
   })
 
   test('observed value should proxy mutations to original (Object)', () => {