Welsh nurses are "not receiving any information on the testing process" for coronavirus, a nursing union has said.
The Royal College of Nursing (RCN) in Wales said members were increasingly frustrated at the lack of detail.
Members deserve to know how the Welsh Government plans to protect individuals "and have their anxiety and stress reduced", its director Helen Whyley said.
The Welsh Government said it was prioritising front-line staff.
Front-line NHS and social care workers with symptoms are among those being tested under the current scheme.
The first of a series of drive-in testing centres was opened in Cardiff on Tuesday.
The RCN in Wales said it has been repeatedly asking the Welsh Government to share the distribution schedule for protective kit and testing. Plaid Cymru leader Adam Price said nurses deserve to have the information.
In a letter to First Minister Mark Drakeford, Ms Whyley said: "Our members are telling us of their increasing frustration in not receiving any information on the testing process.
"It is critical that we act together to provide reassurance."
"The RCN represents over 25,000 registered nurses, nursing students and healthcare support workers in Wales who are currently risking their health to work long and stressful hours in hospitals, care homes and community settings," she wrote.
"Our members deserve to know how the Welsh Government plans to protect people and have their anxiety and stress reduced by being able to access to latest guidance and plans."
"I need to know what plans are in place to test health and social care."
She said the provision of personal protective equipment provision (PPE) was directly affected by the lack of testing, "as with asymptomatic patients or staff it is unclear whether the individual nurse or [health care support worker] should be wearing PPE or not - and this uncertainty leads to stress".
Members in care homes were under particular pressure, she said.
Staff being off work in homes with a small number of staff may result "in the closure of beds or the home itself and the need to transfer vulnerable patients elsewhere at a time of great pressure on the whole health and social care system".
The letter asks how many tests have been undertaken on registered nurses and nursing staff, and for a schedule of the testing process.
Welsh NHS chief executive Dr Andrew Goodall said he would speak later on Thursday afternoon to the leader of the RCN in Wales, to address its members concerns.
Speaking at the Welsh Government's daily coronavirus press conference, Dr Goodall thanked NHS staff for doing a "fantastic" job, and said it was important to provide "reassurance" about the processes that were in place.
Plaid Cymru leader Adam Price said: "Nurses are absolutely crucial in the fight against Covid-19. They work in the community and with patients in the ITUs [intensive therapy units]. They deserve to have this information from the Welsh Government. "The Welsh Government must give a firm commitment today that they will share with them the schedule for testing nurses along with a date all of front-line staff who need PPE will receive it."
A Welsh Government spokesman said: "We published our national plan for testing for Covid-19 this week.
"We have carried out more than 15,000 tests in Wales so far, with one in five tests on those in the care sector.
"We continue to prioritise front-line health and care staff as capacity for testing rapidly increases."