add checkbox unit test (#529)
add checkbox unit test (#529)

* Select: 1.修复可搜索的Select在输入选项中不存在的值时关闭下拉框后未清空手输值的问题;2.支持filterable的可搜索的Select未选中option无法关闭下拉框的问题

* Select: 修复非可搜索条件下选中value为空的option时label值被清空的问题

* add checkbox unit test

sam019/element-react,e1emeb0t/element-react,Hazel54/element-react,e1emeb0t/element-react,e1emeb0t/element-react,CrazyFork/element-react,eleme/element-react,sam019/element-react,eleme/element-react,Hazel54/element-react,Hazel54/element-react,eleme/element-react,CrazyFork/element-react,eleme/element-react,sam019/element-react,CrazyFork/element-react,e1emeb0t/element-react,CrazyFork/element-react,Hazel54/element-react,sam019/element-react