代码报错，请老师解惑

运行testCons()单元测试报错：Error creating bean with name 'injectionService' defined in class path resource [spring-injection.xml]: Unsatisfied dependency expressed through constructor argument with index 0 of type [com.imooc.ioc.injection.dao.InjectionDAO]: Ambiguous constructor argument types - did you specify the correct bean references as constructor arguments?