What is the test for federal jurisdiction in a personal injury case?

Little is needed for a plaintiff to assert a claim sufficient to give the federal court jurisdiction. Where the complaint "is so drawn as to seek recovery directly under the Constitution or laws of the United States," Bell v. Hood, 327 U.S. 678, 681, 66 S.Ct. 773, 775, 90 L.Ed. 939 (1946), the district court must entertain the suit unless the federal claim "clearly appears to be immaterial and made solely for the purpose of obtaining jurisdiction or where such a claim is wholly insubstantial and frivolous," id. at 682-83, 66 S.Ct. at 776.