Test.java

public class ExampleUnitTest {
    
    private boolean mResponseCached = false
    public void testCachingStrategy(){
        MockManagerDelegate mockDelegate = new MockManagerDelegate();
        ApplicationFactory.setInstance(mockDelegate);
        mockDelegate.setCachingManager(new CachingManager(){
            @Override
            void cacheSimpleResponse(Response response) {
                mResponseCached = true;
            }
        });
        MyViewModel testingModel = new MyViewModel();
        testingModel.retrieveSomeValue("someValue");
        Assert.assertTrue(mResponseCached);
    }

    public class MyViewModel {
        private Retrofit retrofit = ApplicationFactory.getRetrofitClient();
        private ManagerDelegate managerDelegate = ApplicationFactory.getManagerDelegateImpl();

        private Observable<Response> retrieveSomeValue(String param) {
            RetrofitClient client = retrofit.create(RetrofitClient.class);
            Observable<Response> request = client.doRequest(param);
            request.subscribe(response ->{
                managerDelegate.getCachingManager().cacheSimpleResponse(response);
            });

            //by returning the "promise" of this network request we can allow some other component of the app to do the routing for us.
            return request;
        }
    }
}