It is a footballing revolution that has not happened in a hurry but it is happening. Yesterday at a rain-shrouded St Mary's, home of Southampton, goal-line technology moved a step closer to being introduced seven years after it was first put to the test. It is not, though, going to be a sprint finish and it remains unlikely any system will be in place in time for the start of next season.

The final decision on whether Fifa will allow the technology to be introduced will come in Kiev on 2 July, the day after the final of Euro 2012. Provided at least one of the two systems under consideration has passed the final stage of testing – which is probable – then it seems certain its use will be approved. With the European domestic season kicking off in August – the Premier League begins on 18 August – neither company, Hawk-Eye or GoalRef, is confident of equipping an entire league in time.

The first league-wide use of technology is likely to come in the next Major League Soccer season in the US, which starts in March. Its first use in Britain could be for England's qualifying games for the 2014 World Cup this autumn. The Football Association has been a keen advocate of goal-line technology, while the Premier League would also look to install it once ready.

"It will take that doubt out of that one decision," said Neale Barry, the FA's head of senior refereeing development, who will advise the FA on whether to vote in favour of its introduction. "Whether a goal has been scored or not is the most important moment of a football match. I haven't come across a referee yet who is not in favour. This is very black-and-white, the ball either crossed the line or it didn't. It's not a matter of opinion. If it works I think every ref will welcome it."

If it works; yesterday marked the first day of the final stage of testing for Hawk-Eye. A handful of men in rain jackets huddled beneath a blue tent laid on the St Mary's pitch. From the stands seven cameras were trained on one goal where there was stood a wooden dummy against which a ball was fired. Today real players will be used to check whether bundles of bodies can obscure the cameras and next Wednesday the Hampshire County Cup final will test it in match conditions.

In the stands sat Barry and three other referees, one from each of the home nations. They will also observe the GoalRef system later this month or next. The German/Danish company are to conduct tests during Danish top-flight games. If both companies reach the standard set by Fifa, leagues and federations will be free to chose either system.

"The testing process is exceptionally rigorous," said Steve Carter, Hawk-Eye's managing director. "If Hawk-Eye or GoalRef passes this, every football fan can sleep at night knowing that an excellent technology is going to be used to make decisions."

The two systems are very different, although both are required to transmit a decision within a second to a special watch worn by the referee. GoalRef uses a magnetic field in the goalmouth and three bands in the ball – the precise details of what's in the ball remain a closely guarded secret because of commercial sensitivities. The company that is approved by Fifa stands to reap a healthy financial reward, after paying what the governing body terms a minimal administration fee, so both are reluctant to talk costs or reveal full details of how their systems work.

Cost is an important factor. GoalRef is cheaper and easier to maintain. A figure of £250,000 has been reported for Hawk-Eye but Carter refused to talk figures. He did admit his company have spent millions of pounds over the course of five years on the project.

Hawk-Eye, which has proved a success in tennis and cricket, uses 14 cameras. When the technology was first developed, each could cost as much as €300,000 but that price has fallen over the years and the company insist the cost of installing a system, which also has to be maintained, will continue to fall. As technology develops, Hawk-Eye would hope to reduce it to two cameras at each end.

In tennis, the Hawk-Eye system is sponsored at each tournament that uses it – some make a profit on installing it – but that would not currently be an option as Fifa insist that there will be no replays in football nor the releasing of any pictures or graphics to broadcasters.