On Thursday night it was announced promoters for Canberra’s Groovin the Moo festival had agreed to the pill testing trial.

But important questions about how this would work were left unanswered on Friday, such as exactly how the testing area and wider festival would be policed.

However, late on Friday the ACT government did confirm that pills would be tested using an infrared spectrophotometer.

It is not clear what will happen to someone caught with drugs outside the pill testing area, how big the amnesty zone will be, or whether festival goers will be drug tested at police checkpoints on the way home.

The announcement came after intense pressure on festival organisers to allow drug testing to go ahead.

On Friday ACT Health Minister Meegan Fitzharris said the government did not make any concessions to organisers to convince them to let the trial occur, despite being given a list of demands early in the negotiations.

"This is a significant milestone for harm reduction in drug policy, it’s really important to note that it doesn't in any way condone illicit drug use but it is an important harm minimisation measure to make sure people have information they wouldn’t otherwise have so they can make better decisions about their own health," Ms Fitzharris said.

Federal Labor MP Andrew Leigh said his colleagues were watching the trial closely although a spokesman for Federal Health Minister Greg Hunt said pill testing was not Commonwealth policy and there were no plans to change that.

"My Labor colleagues and I want these events to be fun, not fatal," Dr Leigh  said.

Chief Minister Andrew Barr was less enthusiastic when he appeared on ABC radio earlier on Friday morning.

“It’s a trial so it will be what it will be,” he said.

“I don't have a view ahead of it. It’s not an issue I’m particularly passionate about one way or the other, no, but I’m happy for this process to proceed."

ACT opposition legal affairs spokesman Jeremy Hanson said there were too many unanswered questions about the trial, including who would be legally responsible should an adverse reaction occur.

He said he had spoken to frontline police who were "incredibly frustrated" with the government for supporting it.

"They are horrified about what’s happening because they’re out there trying to stop the drug trade, trying to stop drug dealers and trying to stop younger people from taking drugs, and this is sending exactly the opposite message," he said.

Mr Hanson also said testing drugs would give festival goers the wrong impression it was safe to take if the pills if the checks found they were pure, and not cut with other substances.

"What I fear is someone is going to take a tablet, thinking that it’s safe when it isn't and get very sick. If that happens it will be on this government’s head," Mr Hanson said.

Ms Fitzharris said the Canberra Liberals' position was "ill-informed" and people would be given information about their own liability.

ACT Health said testing would be held in an enclosed facility next to first aid and ambulance services.

Members of the STA-SAFE consortium responsible for conducting testing did not respond to requests for comment.

One member said festival promoters Cattleyard Promotions had imposed a media ban, while Cattleyard funnelled questions back to ACT Health.

ACT Policing said there would be a “health precinct” at Groovin the Moo, understood to be the area in which testing would be done, and that this area would not be targeted.

“ACT Policing will not actively target the health precinct or their users in line with well-established protocols with ACT Health facilities,” a spokesman said.

“As a police force, we will continue to target and investigate the sale and supply of illicit drugs.”

Police have voiced support for pill testing and harm reduction strategies in the lead-up to Sunday’s event.

Public Health Association chief executive Michael Moore congratulated the ACT government and police for forging ahead with the pill testing trial.

“I hear people saying this in some way condones drug use. The same arguments we’ve heard around needle and syringe programs,” he said.

“Just as these programs have saved thousands of lives, I think that this intervention will also be one that does save lives. The evidence is clear.”

Australian Drug Law Reform Foundation president Dr Alex Wodak described the decision as a “milestone”, although remained sceptical about whether it would happen.

“I’m aware that the ACT government says it’s going ahead. But I don’t think we should count our chickens before they are hatched,” he said.

“This area has got a terrible track record of last minute obstacles appearing from nowhere.

“My hopes have been dashed so often, that I try not to expect too much.”

Harm minimisation advocates have long pushed for pill testing at festivals, arguing it had been effective in protecting young people when implemented overseas.

A letter co-signed by a suite of health experts and advocates sent to Cattleyard this month said allowing the trial would "potentially save lives".

"Research shows that pill-testing helps young people avoid the dangers of unknown and contaminated drugs, and provides an opportunity for drugs to be disposed of before lives are put at risk," the letter said.