SAN FRANCISCO — In the running legal controversy over what rights workers should have in the “gig economy,” ride-hailing giants Uber and Lyft have grabbed many of the headlines­—so far without any resolution in court. But a sleeper case against the food delivery app GrubHub could be the one that finally puts the issue to the test.

On Thursday, U.S. Magistrate Judge Jacqueline Corley of the Northern District of California indicated she would let an individual employment case head toward trial in September against GrubHub on behalf of a former delivery driver named Raef Lawson. At a hearing, Corley noted that it could be something of a bellwether case for a long-percolating issue.