AbstractTransactionalSpringContextTests疑问
AbstractTransactionalSpringContextTests为每个Test方法添加了事务功能，极大方便了测试。根据官方资料：
AbstractTransactionalSpringContextTests depends on a PlatformTransactionManager bean being defined
in the application context. The name doesn't matter, due to the use of autowire by type.
如果applicationContext中定义了两个或者多个PlatformTransactionManager，会发生什么？AbstractTransactionalSpringContextTests如何去选择采用哪中事务管理？
