Change in policy has been prompted by the latest evidence.
All residents and staff in Welsh care homes which have outbreaks of coronavirus will be tested.
Previously, only those who were showing symptoms or who were being moved into a care home were being tested for Covid-19 were offered testing.
Health Minister Vaughan Gething says the latest evidence prompted a change of policy.
We're told 8 new mobile testing units which are being rolled out this week and home testing kits - when they become available - will be focused towards care homes to make sure testing is easily available.
Both the Welsh Conservatives and Plaid Cymru have called the move a 'u-turn' and are calling for testing for staff and residents in all care homes - in line with England.
Health Minister Vaughan Gething said: "Our national testing plan has two main aims – to reduce the harm caused by coronavirus and to help people and professionals get back to their normal daily lives.
"We are learning more about coronavirus every day – the evidence is constantly changing and emerging and we keep it under constant review.
"At the moment, the evidence does not support the blanket testing of everyone who does not have symptoms.
"But, in a care home setting, where there are some people who have symptoms of coronavirus and others who do not, testing everyone, including those who do not, does have a purpose – we will be doing this to help manage outbreaks."
Reacting to the change its policy on testing in care homes, Plaid Cymru Leader Adam Price said:
"This U-turn follows scrutiny and criticism from Plaid Cymru over their refusal to test asymptomatic residents and staff. While it is a step in the right direction, the logic behind testing only in larger care homes and ‘potentially those neighbouring ones with outbreaks’ is questionable.
"Why not test staff and residents in every home?
"Welsh Government says the evidence does not support ‘blanket testing’. They should publish that evidence swiftly so that it can be scrutinised to see how and why it differs from international evidence and best practice that promotes universal testing of all care home staff and residents."