Testing, one of the methods to combat the COVID-19 outbreak, is highly recommended in all countries. Empirical studies on how testing relates to the control of new cases will help highlight the importance of testing in efforts to combat the epidemic. Therefore, this study aims to investigate the relationship between COVID-19 testing and COVID-19 cases. We use panel autoregressive distributed lag analysis to test the effect of COVID-19 test number on the COVID-19 new cases. The data of the study cover the period from March 19, 2020, to May 01, 2020, for 14 OECD countries. Data were obtained from the https://ourworldindata.org/coronavirus website. According to the results, this study shows that increasing the COVID-19 test number will help to reduce new COVID-19 cases. On the other hand, increase in the test number per thousand will probably not contribute to reducing new COVID-19 cases, because countries do not already test by random selection, and even if they do, it will not contribute to detection and isolating of the new cases without identifying risky groups.