chore(test): add some cases with snapshot (#966)

tests/proxyMap.test.tsx

@@ -1,7 +1,7 @@
 import { StrictMode } from 'react'
 import { fireEvent, render, waitFor } from '@testing-library/react'
 import { describe, expect, it, vi } from 'vitest'
-import { proxy, useSnapshot } from 'valtio'
+import { proxy, snapshot, useSnapshot } from 'valtio'
 import { proxyMap, proxySet } from 'valtio/utils'
 
 const initialValues = [
@@ -319,3 +319,18 @@ describe('proxyMap internal', () => {
     ).toBe(false)
   })
 })
+
+describe('snapshot', () => {
+  it('should not change snapshot with modifying the original proxy', async () => {
+    const state = proxyMap([
+      ['key1', {}],
+      ['key2', { nested: { count: 1 } }],
+    ])
+    const snap1 = snapshot(state)
+    expect(snap1.get('key1')).toBeDefined()
+    state.get('key2')!.nested!.count++
+    const snap2 = snapshot(state)
+    expect(snap1.get('key2')!.nested!.count).toBe(1)
+    expect(snap2.get('key2')!.nested!.count).toBe(2)
+  })
+})

tests/snapshot.test.ts

@@ -69,6 +69,16 @@ it('should create a new proxy from a snapshot', async () => {
   expect(state2.c).toBe(0)
 })
 
+it('should not change snapshot with modifying the original proxy', async () => {
+  const state = proxy({ obj1: {}, obj2: { nested: { count: 1 } } })
+  const snap1 = snapshot(state)
+  expect(snap1.obj1).toBeDefined()
+  state.obj2.nested.count++
+  const snap2 = snapshot(state)
+  expect(snap1.obj2.nested.count).toBe(1)
+  expect(snap2.obj2.nested.count).toBe(2)
+})
+
 describe('snapsoht typings', () => {
   it('converts object properties to readonly', () => {
     expectType<