java.lang.UnsupportedOperationException: elapsedRealtime is native
	at android.os.SystemClock.elapsedRealtime(SystemClock.java)

@PrepareForTest({ ScreenUtil.class, NetUtil.class})

PowerMockito.mockStatic(NetUtil.class);

    @Test
    public void test0() throws Exception {
        MockHeartAction action = new MockHeartAction();
        Context context = PowerMockito.mock(Context.class);
        //PowerMockito.doReturn("networkTag").when(NetUtil.getNetworkTag(context));//代码[1.2] 
       // PowerMockito.when(NetUtil.getNetworkTag(context)).thenReturn("networkTag");//代码[1.1] 
       PowerMockito.when(NetUtil.getNetworkTag(Mockito.any(Context.class))).thenReturn("networkTag");//代码[1.3] 
        String string = NetUtil.getNetworkTag(context);
        LogUtil.d("==="+string);
        
       ClassA  a = new ClassA();
       a.test();
    }

   class A{
      public void a{
         String networkTag = NetUtil.getNetworkTag(heartContext.getContext());
           LogUtil.d(TAG, "===XXX" + networkTag);
      }
   }

// 执行代码[1.2]
PowerMockito.doReturn("networkTag").when(NetUtil.getNetworkTag(context));//代码[1.2]
//报的异常
org.mockito.exceptions.misusing.UnfinishedStubbingException: 
Unfinished stubbing detected here:
-> at com.xtc.im.core.push.heartbeat.state.ActiveStateTest.heartbeat0(ActiveStateTest.java:59)

E.g. thenReturn() may be missing.
Examples of correct stubbing:
    when(mock.isOk()).thenReturn(true);
    when(mock.isOk()).thenThrow(exception);
    doThrow(exception).when(mock).someVoidMethod();
Hints:
 1. missing thenReturn()
 2. you are trying to stub a final method, you naughty developer!
 3: you are stubbing the behaviour of another mock inside before 'thenReturn' instruction if completed


	at org.powermock.core.MockGateway.doMethodCall(MockGateway.java:124)
	at org.powermock.core.MockGateway.methodCall(MockGateway.java:63)
	at com.xtc.im.core.common.utils.NetUtil.getNetworkTag(NetUtil.java)