### Question:
ObjectProviderUtils { public static <T> ObjectProvider<T> singleton(ObjectProvider<T> inner) { return new SingletonProvider<T>(inner); } private  ObjectProviderUtils(); static ObjectProvider<T> bean(Class<T> beanClass); static ObjectProvider<T> cloning(T prototype); static ObjectProvider<T> constant(T value); static ObjectProvider<T> nullValue(); static ObjectProvider<T> singleton(ObjectProvider<T> inner);  }### Answer:
@Test public void testSingleton() throws Exception { assertTrue(ObjectProviderUtils.singleton(new ConstantProvider<Object>("Hello")) instanceof SingletonProvider); }