It’s time to test the waters. Washington is reportedly set to sail warships close to artificial islands that China has built in the marginal sea between Singapore and Taiwan. Beijing says it has territorial control of the area, and the U.S. maneuver signals Washington’s rejection of that claim. American ships will reportedly venture — for the first time since 2012 — within the 12-mile maritime zone the Chinese assert is theirs. The move, expected in the next two weeks, is likely to further strain relations between the countries.