Verifying Embedded Graphics Libraries leveraging Virtual Prototypes and Metamorphic Testing

Embedded graphics libraries are part of the firmware of embedded systems and provide complex functionalities optimized for specific hardware. After unit testing of embedded graphics libraries, integration testing is a significant challenge, in particular since the hardware is needed to obtain the output image as well as the inherent difficulty in defining the reference result. In this paper, we present a novel approach focusing on integration testing of embedded graphic libraries. We leverage Virtual Prototypes (VPs) and integrate them with Metamorphic Testing (MT). MT is a software testing technique that uncovers faults or issues in a system by exploring how its outputs change under predefined input transformations, without relying on explicit oracles or predetermined results. In combination with virtualizing the displays in VPs, we even eliminate the need for physical hardware. This allows us to develop a MT framework automating the verification process. In our evaluation, we demonstrate the effectiveness of our MT framework. On an extended RISC-V VP for the GD32V platform we found 15 distinct bugs for the widely used TFT eSPI embedded graphics library, confirming the strength our approach.