Cyber-physical system (CPS) development tool chains are widely used in the design, simulation, and verification of CPS data-flow models. Commercial CPS tool chains such as MathWorks' Simulink generate artifacts such as code binaries that are widely deployed in embedded systems. Hardening such tool chains by testing is crucial since formally verifying them is currently infeasible. Existing differential testing frameworks such as CyFuzz can not generate models rich in language features, partly because these tool chains do not leverage the available informal Simulink specifications. Furthermore, no study of existing Simulink models is available, which could guide CyFuzz to generate realistic models.To address these shortcomings, we created the first large collection of public Simulink models and used the collected models' properties to guide random model generation. To further guide model generation we systematically collected semi-formal Simulink specifications. In our experiments on several hundred models, the resulting SLforge generator was more effective and efficient than the state-of-the-art tool CyFuzz. SLforge also found 8 new confirmed bugs in Simulink. CCS CONCEPTS• Software and its engineering → Model-driven software engineering; Software testing and debugging; KEYWORDSCyber-physical systems, differential testing, tool chain bugs ACM Reference Format:

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User interface development typically starts with freehand sketching, with pen on paper, which creates a big gap in the software development process. Recent advances in deep neural networks that have been trained on large sketch stroke sequence collections have enabled online sketch detection that supports many sketch element classes at high classification accuracy. This paper leverages the recent Google Quick, Draw! dataset of 50M sketch stroke sequences to pre-train a recurrent neural network and retrains it with sketch stroke sequences we collected via Amazon Mechanical Turk. The resulting Doodle2App website offers a paper substitute, i.e., a drawing interface with interactive UI preview and can convert sketches to a compilable single-page Android application. On 712 sketch samples Doodle2App achieved higher accuracy than the state-of-the-art tool Teleport. A video demo is at https://youtu.be/P4sb0pKTNEY CCS CONCEPTS • Software and its engineering → Software prototyping; • Humancentered computing → User interface toolkits.

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