The first Lightweight IoT blog post by Hatem Oueslati of IoTerop highlighted the importance of interoperability as fundamental to the success of the Internet of Things (IoT). Today, most IoT solutions available are proprietary and incompatible with one another. Costs incurred due to fragmentation are too high for suppliers, developers and users. But even if developers do use standardized solutions to build their products, how will they know their solutions will be interoperable with other products in the market? The answer is interoperability testing.