RoutingPlan { public boolean isEmpty() { return depot == null && vehicles.isEmpty(); } RoutingPlan(
            Distance distance,
            List<Vehicle> vehicles,
            Location depot,
            List<Location> visits,
            List<RouteWithTrack> routes); static RoutingPlan empty(); Distance distance(); List<Vehicle> vehicles(); List<RouteWithTrack> routes(); List<Location> visits(); Optional<Location> depot(); boolean isEmpty();  }
@Test void isEmpty() { assertThat(RoutingPlan.empty().isEmpty()).isTrue(); assertThat(new RoutingPlan(Distance.ZERO, emptyList(), depot, emptyList(), emptyList()).isEmpty()).isFalse(); assertThat(new RoutingPlan(Distance.ZERO, vehicles, null, emptyList(), emptyList()).isEmpty()).isFalse(); assertThat(new RoutingPlan(Distance.ZERO, vehicles, depot, emptyList(), singletonList(emptyRoute)).isEmpty()) .isFalse(); }