feat: manually mirror opencoze's code from bytedance

Change-Id: I09a73aadda978ad9511264a756b2ce51f5761adf

frontend/packages/common/chat-area/text-grab/__tests__/find-last-child-node.test.ts

@@ -0,0 +1,48 @@
+/*
+ * Copyright 2025 coze-dev Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+ 
+import { findLastChildNode } from '../src/utils/helper/find-last-child-node';
+
+describe('findLastChildNode', () => {
+  it('should return the last child node of a nested node structure', () => {
+    // 创建一个嵌套的节点结构
+    const parentNode = document.createElement('div');
+    const childNode1 = document.createElement('span');
+    const childNode2 = document.createElement('p');
+    const lastChildNode = document.createElement('a');
+
+    parentNode.appendChild(childNode1);
+    childNode1.appendChild(childNode2);
+    childNode2.appendChild(lastChildNode);
+
+    // 调用 findLastChildNode 函数
+    const result = findLastChildNode(parentNode);
+
+    // 验证结果是否为最深层的子节点
+    expect(result).toBe(lastChildNode);
+  });
+
+  it('should return the node itself if it has no children', () => {
+    // 创建一个没有子节点的节点
+    const singleNode = document.createElement('div');
+
+    // 调用 findLastChildNode 函数
+    const result = findLastChildNode(singleNode);
+
+    // 验证结果是否为节点本身
+    expect(result).toBe(singleNode);
+  });
+});