According to Harvard estimates, 500,000 to 700,000 tests have to be performed before the U.S. can safely reopen. That level of testing is necessary to identify the majority of infected people and isolate them from healthy people. Testing could reduce the rate of positives, which is fundamental for opening an economy.
https://www.nytimes.com/interactive/2020/04/17/us/coronavirus-testing-states.html