Testing is widely seen as one core element of a successful strategy to curtail the COVID-19 pandemic and many countries have increased their efforts to provide testing at large scale. As most democratic governments refrain from enacting mandatory testing, a key emerging challenge is to increase voluntary participation. Using behavioural economics insights complemented with data from a novel survey in the US and a survey experiment in Luxembourg, we examine behavioural factors associated with the individual willingness to get tested (WTT). In our analysis, individual characteristics that correlate positively with WTT include age, altruism, conformism, the tendency to abide by government-imposed rules, concern about contracting COVID-19, and patience. Risk aversion, unemployment, and conservative political orientation correlate negatively with WTT. Building on and expanding these insights may prove fruitful for policy to effectively raise people's propensity to get tested.