As of 16-August-2018 this appears to be an issue. Note the following apex test method.
@isTest static void myTestMethod() {
System.Test.StartTest();
String jobId = System.schedule(xxx, xxx, xxx);
System.Test.StopTest();
//Assetion failed. Expected "Finished" actual "Waiting"
System.assertEquals('Finished', [select State from CronTrigger where Id = :jobId ][0].State);
}