Sadie Whitcombe turned up for her 8.10am appointment at Russells Hall Hospital today and was left waiting in her car for two hours.
The 51-year-old from Wordsley is having a procedure at the hospital, so she is required to have a Covid-19 test before this can take place.
But despite being just fourth in the queue for the appointment-only tests, she was left waiting until there were about 50 cars behind her, she said.
"I've got an operation on Thursday at Russells Hall Hospital so I had a Covid test booked for 8.10am," she said.
"I turned up about 8am I was the fourth person in the queue, at 9.10am nothing was happening and there was about 30 cars behind me.
"I rang the hospital and they said they're probably running behind you'll have to wait, I said it's not moved since I've been here.
"At 9.45am there's about 50 cars and the consultant's secretary told me there was no testing today, then three people came out in suits and said there's no tests today, go home.
"I got half way home and they called me and asked me to come back, so I went back but couldn't get near the place, there were about 70 cars waiting then.
"Everybody was kicking off, nobody knew anything, security came out to see what the problem was as people were beeping.
"I went home and they've booked me a test for tomorrow morning.
"It was absolutely farcical."
Diane Wake, chief executive, The Dudley Group NHS Foundation Trust, said: "We are sorry that patients arriving for Covid testing today experienced a delay. This service is for our patients who are scheduled for planned procedures/operations. It is not a public testing centre.
"This is not how we want to treat our patients who are attending for screening prior to their treatment. Unfortunately we had staff shortages at late notice and this meant we needed to reallocate other staff from within the trust who are trained in swabbing.
"We did not want patients to have to wait while we sorted the problem and so sent them home. Patients have returned today for their swabs and we have sincerely apologised to our patients.
"This is the first time this has happened and we have put measures in place to make sure it does not happen again."