General Motors Co. GM 0.26 % and Lyft Inc. will begin testing a fleet of self-driving Chevrolet Bolt electric taxis on public roads within a year, a move central to the companies’ joint efforts to challenge Silicon Valley giants in the battle to reshape the auto industry. The plan is being hatched a few months after GM invested $500 million in Lyft , a ride-hailing company that rivals Uber Technologies Inc. The program will rely on technology the being acquired as part of GM’s separate $1 billion planned purchase of San Francisco-based Cruise Automation Inc., which has been working on self-driving technology for about two years. Details of the autonomous-testing program are still being worked out, according to a Lyft executive, but it will include real customers and based in a yet-to-be disclosed city. […]