The first pilot scheme starting on Friday and offered to everyone in Liverpool, including schoolchildren. Tests will be provided in schools, universities, hospitals and at home.
If the two-week pilot succeeds, millions of tests will be offered in cities across the country between now and Christmas, Mr Johnson said.
On Monday, he said rapid turnaround tests were key, with regular testing able to identify those carrying the virus and break chains of transmission, with a “steady but massive expansion” in testing planned.
The rollout of mass testing and the “real prospect” of a vaccine in the first quarter of next year gave grounds for optimism, Mr Johnson told the Commons.
“I believe that these technical developments, taken together, will enable us to defeat this virus by the spring as humanity has defeated every other infectious disease,” he said.
Amid fury from Tory MPs, he insisted that, if approved by MPs, the national lockdown would automatically expire next month and the Commons “will have a vote to agree the way forward”.
The plans for “whole city testing” are part of the £100 billion “Moonshot” strategy which aims to see 10 million people tested a day regardless of whether they have symptoms.
Meanwhile, Jacob Rees-Mogg suggested on Monday that MPs could be tested for coronavirus every week as Premier League footballers are. The Leader of the House said the Commons Commission had held a “discussion on testing” and the idea was “something that’s under consideration”.
Case rates in the North-West are among the highest in the country, with Liverpool and Merseyside categorised as Tier 3, with the toughest restrictions, when the three-tier system was introduced.