### Question:
ObjectPoolHelper { public final void setObjectPool(final GenericObjectPool<T> objectPool) { notNull(objectPool); this.objectPool = objectPool; } ObjectPoolHelper(final ObjectFactory<T> objectFactory); T getObject(); void returnObject(final T engine); final void setObjectPool(final GenericObjectPool<T> objectPool); void destroy();  }### Answer:
@Test(expected = NullPointerException.class) public void cannotSetNullObjectPool() throws Exception { final ObjectPoolHelper<Integer> pool = new ObjectPoolHelper<Integer>(new ObjectFactory<Integer>() { @Override public Integer create() { return 3; } }); pool.setObjectPool(null); }