I'm trying to mock arraylist to verify the add method but I'm getting the message:

```
FAILED: testInit
Wanted but not invoked:
arrayList.add(<any>);
-> at AsyncRestTemplateAutoConfigurationTest.testInit(AsyncRestTemplateAutoConfigurationTest.java:95)
Actually, there were zero interactions with this mock.

```

The test class I've used is:

```
@Test
    public void testInit() throws Exception {

        ArrayList<AsyncClientHttpRequestInterceptor> interceptors = Mockito.mock(ArrayList.class);

        PowerMockito.whenNew(ArrayList.class).withAnyArguments()
                .thenReturn(interceptors);

        Mockito.stub(interceptors.add(Mockito.any())).toReturn(true);
        asyncRestTemplateAutoConfiguration.init();

        Mockito.verify(interceptors).add(Mockito.any());
    }

```

The actual tested code is:

```
List<AsyncClientHttpRequestInterceptor> interceptors = new ArrayList<>(interceptors);
    interceptors.add(new TracingAsyncRestTemplateInterceptor(tracer));

```

I've declared the test class with 

```
@RunWith(PowerMockRunner.class)
@PrepareForTest(AsyncRestTemplateAutoConfiguration.class)

```

Where `AsyncRestTemplateAutoConfiguration`is the class, which I'm using to test. Could anyone please tell me what I'm missing?