<jats:title>Abstract</jats:title><jats:p>The increasingly evident role of asymptomatic and pre-symptomatic transmission means testing is central to COVID-19 control, but test sensitivity estimates are low (around 65%). We extend an existing branching process contact tracing model, adding diagnostic testing and refining parameter estimates. Poor test sensitivity potentially reduces the efficacy of contact tracing, due to false-negative results impacting quarantine. We show that, counter-intuitively, faster testing could also reduce operational test sensitivity, exacerbating this effect. If sensitivity-based risks are mitigated, we find that contact tracing can facilitate control, but small changes in the population reproduction number (1·3 to 1·5) could impact contact tracing feasibility.</jats:p>