Detroit Mayor Mike Duggan announced on Friday that the city will start making diagnostic tests available to all employees of “essential” businesses, and to city employees performing essential services.

Why it matters: It’s the first program of its kind, and a model for other cities to follow. And it’s a reminder that testing remains the limiting factor in every facet of our response to the coronavirus.

You may be tired of hearing about testing. You may think it has become an almost myopic focus in a multifaceted crisis. But there is simply no way to work around it, or to put that problem to the side and focus on something else. All roads lead back to testing.

Between the lines: Detroit’s plan to test people who aren’t experiencing symptoms, even if it's just a small group, is critical.

Many parts of the country, though, simply don’t have the capacity to test anyone who isn't feeling sick. That will never be good enough.

Although more rapid tests are becoming available, turnaround times of up to a week increase the risk that people will spread the virus without knowing it.

If you test someone too soon after they’ve contracted COVID-19, they won’t have enough of the virus in their system, resulting in a false negative — which means some infected workers may slip through the cracks even with widespread testing.

Our thought bubble: Every incremental step that brings more people out into the world creates some level of additional risk. We don’t have a vaccine and we can’t stay inside forever, so all we can do is try to find a level of risk that’s manageable.