The unit has opened at Studley Gate Car Park, next to Swanpool Park, in Stourbridge and marks the third walk-through site in the borough.
It comes as part of a Government push to ensure people with symptoms can receive a test locally, with the site accessible without a car.
Health Minister Lord Bethell said: "To respond to the coronavirus, we have built a major testing and tracing system from scratch. We are constantly working to expand and improve it with new technologies and innovations so everyone with symptoms can get a test.
“New walk-in sites like this one makes it even easier to get a test no matter where you live. If you have symptoms of coronavirus, I urge you to book a test today and follow the advice of NHS Test and Trace if you are contacted to protect others and stop the spread of the virus."
Anyone attending an appointment at the walk-through test site will be provided with guidance on getting to and from the test site safely, with additional support for vulnerable groups and people with disabilities.
Baroness Dido Harding, interim executive chairwoman of the National Institute for Health Protection, said: "Walk-through sites offer communities better access to coronavirus testing, so everyone with symptoms can get a test. This new site is part of our ongoing work to expand our testing network across the UK which now has the capacity to process more than 700,000 tests a day. We will continue to expand capacity to improve test turnaround times and push forward testing innovations to make sure anyone who needs a test can get one.
"Please book a test if you have coronavirus symptoms: a new continuous cough, a high temperature and a loss or change in sense of smell or taste, and follow the advice of NHS Test and Trace if you are contacted."
The testing centre is being operated in partnership with Mitie and will offer self-administered tests. Anyone with symptoms can book or order a test at nhs.uk/coronavirus. Those unable to access the internet can call 119 in England.