Hywel Dda have also opened appointment-only centres
Coronavirus Testting Centres have been opened in Neath Port Talbot - just off the M4- and in Carmarthen and Cardigan.
Swansea Bay University Health Board has opened a drive-through testing centre on a former playing field changing rooms.
Hywel Dda Health Board's has opened the other two centres.
People who need to be tested will be able to access it by appointment only, usually through the 111 service.
Home testing will continue in certain circumstances.
Keith Reid, Swansea Bay Director of Public Health, said:
"The demand for testing people for COVID-19 is growing, so it is important that we are able to provide a convenient and safe way to provide tests in a timely way, and which makes the best use of our hard-working staff.
"People who don’t drive or don’t have access to a car can still be tested in their own home.
"We are very grateful to Neath Port Talbot Council for allowing us to use their land to set up the unit.”
Stringent infection control measures are in place at the testing unit, and staff have also been issued with specialist protective clothing.
The testing unit is accessible by appointment only.
Hywel Dda University Health Board’s Director of Public Health Ros Jervis said:
"We are extremely proud of our staff in Hywel Dda University Health Board who are working hard to protect the health of our communities in response to COVID-19.
“We are working with our local, regional and national partners to implement our planned response and stringent infection control measures.
“Like other health boards, we have been undertaking tests for COVID-19 in people’s own homes. The demand for this is likely to get greater and we have planned additional capacity to deal with this by opening our CTUs. This will allow us to undertake far more tests for appropriate patients, who have used the 111 pathway."
“We are grateful for the co-operation of our communities.”
For those wondering if they have Coronavirus, there is now an online COVID-19 symptom checker available.
People are still being warned not to attend their GP surgery, the hospital emergency department or the minor injury unit if they think they have the virus