3.6 调用者的上下文

在Fake类的方法中，可以设置一个Invocation类对象，在该方法被调用时，JMockit会为这个对象传值。这种机制的意义是Fake类可以接触到真实类。因此，Fake类的方法可以得到调用参数，调用次数等信息。

@Test
public void invocation() throws Exception {

   final Subject testSubject = new Subject();

   new MockUp<LoginContext>() {
      @Mock
      void $init(Invocation invocation, String name, Subject subject)
      {
         assertNotNull(name);
         assertSame(testSubject, subject);

         // Gets the invoked instance.
         LoginContext loginContext = invocation.getInvokedInstance();

         // Verifies that this is the first invocation.
         assertEquals(1, invocation.getInvocationCount());
      }

      @Mock
      void login(Invocation invocation)
      {
         // Gets the invoked instance.
         LoginContext loginContext = invocation.getInvokedInstance();

         // getSubject() returns null until the subject is authenticated.
         assertNull(loginContext.getSubject());
      }

      @Mock
      void logout(Invocation invocation)
      {
         // Gets the invoked instance.
         LoginContext loginContext = invocation.getInvokedInstance();

         assertSame(testSubject, loginContext.getSubject());
      }
   };

   LoginContext theFakedInstance = new LoginContext("test", testSubject);
   theFakedInstance.login();
   theFakedInstance.logout();
}