Spring is designed so that applications using it are as easy as possible to test

As far as possible, application objects will be POJOs, and POJOs are easy to test; dependence on Spring APIs will normally be in the form of interfaces that are easy to stub or mock. Unlike the case of JNDI, for example, stubbing or mocking is easy; unlike the case of Struts, for example, application classes are seldom forced to extend framework classes that themselves have complex dependencies.