fix toJSON value

tests/doc.tests.js

@@ -40,6 +40,7 @@ export const testToJSON = tc => {
 
   const arr = doc.getArray('array')
   arr.push(['test1'])
+  t.compare(arr.toJSON(), ['test1'])
 
   const map = doc.getMap('map')
   map.set('k1', 'v1')

tests/undo-redo.tests.js

@@ -1,4 +1,4 @@
-import { init, compare, applyRandomTests, Doc } from './testHelper.js' // eslint-disable-line
+import { init, compare, applyRandomTests, Doc, UndoManager } from './testHelper.js' // eslint-disable-line
 
 import * as Y from '../src/index.js'
 import * as t from 'lib0/testing'