Unit testing using spock for Amazon Dynamodb

I am new in using dynamodb, and I tried to do uniting testing on one of the method.

When I try to mock

DeleteItemSpec deleteItemSpec = new DeleteItemSpec().withPrimaryKey(new PrimaryKey("id", id, "date", date).withConditionExpression("id = :id")

It returns NPE. How can I mock this with many properties?

Sorry for such a dumb question, but tried whole night for solution.

public void delete(String id) {
    Item item = null;
    Iterator<Item> iterator = getId(id);
    while (iterator.hasNext()) {
        item = iterator.next();
        DeleteItemSpec deleteItemSpec = new DeleteItemSpec()
            //get null pointer on below line
            .withPrimaryKey(new PrimaryKey("id", id, "date", item.getString("date")))
            .withConditionExpression("id = :id")
            .withValueMap(new ValueMap()
            .withString(":id", id))
            .withReturnValues(ReturnValue.ALL_OLD);

        try {
            table.deleteItem(deleteItemSpec);
        } catch (Exception e) {e.getLocalizedMessage(), e);
            throw new dynamoDBException("...")
        }
    }
}