Months into the COVID-19 pandemic, the United States has finally moved from relying entirely on a single, flawed diagnostic test to having what may soon be an onslaught of testing options available from private entities. The U.S. Food and Drug Administration over the last three weeks has authorized the emergency use of more than 20 diagnostic tests for the novel coronavirus known as SARS-CoV-2. Those add to the hundreds of tests that researchers are developing globally. The Foundation for Innovative New Diagnostics (FIND) in Geneva, Switzerland keeps a running global list of COVID-19 tests that, as of 3 April, neared 400. To help our readers sort through the deluge of diagnostics, here, we provide a simple explainer on coronavirus testing.