NEW YORK — McDonald's says it plans to start testing seasoned french fries at select U.S. locations starting Friday.

The world's biggest hamburger chain says the test of its "Shakin' Flavor Fries" will take place at restaurants in northern California and St. Louis. Customers will be able to choose garlic Parmesan, spicy Buffalo or zesty ranch flavors.

McDonald's spokeswoman Lisa McComb says the idea came from the company's "Shake Shake" seasoned fries, which debuted in Hong Kong in 2005 before spreading to countries including China, India and Australia.

The website GrubGrade.com had published photos of the seasoned fries at a McDonald's in Stockton, California, on Thursday. The packaging includes directions telling people how to pour the seasoning onto french fries in a bag and shake them.

"As with all tests, we aren't in a position to draw conclusions or make assumptions about the test since it is just beginning but we hope our customers in these two markets enjoy the new flavors," McComb said in an email.

McDonald's, based in Oak Brook, Illinois, has more than 35,000 locations around the world.