test(dropdown): add dropdown test

[Isabella327]

🤔 这个 PR 的性质是？

• 日常 bug 修复
• 新特性提交
• 文档改进
• 演示代码改进
• 组件样式/交互改进
• CI/CD 改进
• 重构
• 代码风格优化
• 测试用例
• 分支合并
• 其他

🔗 相关 Issue

#1280

💡 需求背景和解决方案

test(dropdown): add dropdown test

📝 更新日志

• fix(组件名称): 处理问题或特性描述 ...

• 本条 PR 不需要纳入 Changelog

☑️ 请求合并前的自查清单

⚠️ 请自检并全部勾选全部选项。⚠️

• 文档已补充或无须补充
• 代码演示已提供或无须提供
• TypeScript 定义已补充或无须补充
• Changelog 已提供或无须提供

[github-actions]

[codecov-commenter]

Codecov Report

Merging #1352 (543f732) into develop (3eae14b) will increase coverage by 0.66%.
The diff coverage is 66.19%.

@@             Coverage Diff             @@
##           develop    #1352      +/-   ##
===========================================
+ Coverage    59.88%   60.54%   +0.66%     
===========================================
  Files         1017     1030      +13     
  Lines        17807    17945     +138     
  Branches      4085     4122      +37     
===========================================
+ Hits         10663    10865     +202     
+ Misses        7144     7080      -64     

Impacted Files	Coverage Δ
src/_util/helper.ts	21.62% <ø> (-19.45%)	⬇️
src/config-provider/_example/global.jsx	100.00% <ø> (ø)
src/date-picker/hooks/useRange.tsx	37.66% <ø> (+0.48%)	⬆️
src/date-picker/hooks/useSingle.tsx	40.74% <ø> (+0.74%)	⬆️
src/dialog/Dialog.tsx	76.92% <ø> (ø)
src/dialog/RenderDialog.tsx	60.34% <0.00%> (-1.79%)	⬇️
src/dialog/plugin.tsx	19.35% <ø> (ø)
src/form/formModel.ts	57.44% <ø> (ø)
src/message/Message.tsx	17.10% <ø> (ø)
src/popup/Popup.tsx	92.30% <ø> (ø)
... and 48 more

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