This causal DAG and BN describes the interactions of pre-testing, specimen collection and laboratory procedures and RT-PCR platform factors, and their impact on the presence and quantity of virus and thus the test result and its interpretation. By setting the input variables as ‘evidence’ for a given subject and preliminary parameterisation, four scenarios were simulated to demonstrate potential uses of the model. The core value of this model is a deep understanding of the total testing cycle, bridging the gap between a person's true infection status and their test outcome. This model can be adapted to different settings, testing modalities and pathogens, adding much needed nuance to the interpretations of results. This model presents as one of many models constituting causal knowledge base established via the COVID-I project. Please find the [COVID-I Project Overview here][1]. ---------- **PROJECT UPDATES** **2021/06/23:** Peer-reviewed [publication][2] is available online. **2020/12/01:** We have now also uploaded our laboratory testing model paper to preprint and is now available. https://www.medrxiv.org/content/10.1101/2020.11.30.20241232v1 **2020/11/30:** We have submitted our laboratory testing model paper for publication. **2020/11/18:** The laboratory testing model has now been uploaded to OSF. https://osf.io/t834y/?view_only=afbdfb3e22c2406cad1ae142a3e5a3b2 **2020/07/20:** Elicitation workshop on the laboratory testing model with Jen Kok and Matthew O'Sullivan. **2020/06/26:** Group elicitation workshop #2 about diagnosis for the laboratory testing model. **2020/05/29:** Group elicitation workshop about diagnosis for the laboratory testing model. **2020/04/27:** The COVID-Intelligence Project is now on OSF! We will be using OSF to engage with our community of experts to support in knowledge elicitation and building the Bayesian Networks that will drive the Decision support solution. OSF will also serve as a source of open access to the elicitation and models developed by this project. [1]: https://osf.io/t834y/wiki/Project%20Overview/?view_only=afbdfb3e22c2406cad1ae142a3e5a3b2 [2]: https://doi.org/10.1017/S0950268821001357