--- a/src/ai/api/ai_sign.hpp	Tue Mar 27 10:33:42 2007 +0000
+++ b/src/ai/api/ai_sign.hpp	Tue Mar 27 11:55:16 2007 +0000
@@ -72,6 +72,8 @@
 	 * @pre location is always positive and below AIMap::GetMapSize()
 	 * @pre text is not NULL and non-empty, i.e. length is positive.
 	 * @return the SignID of the build sign (use IsValidSign() to check for validity).
+	 *   In test-mode it returns 0 if successful, or any other value to indicate
+	 *   failure.
 	 */
 	SignID BuildSign(TileIndex location, const char *text);
 };

--- a/src/ai/api/ai_vehicle.hpp	Tue Mar 27 10:33:42 2007 +0000
+++ b/src/ai/api/ai_vehicle.hpp	Tue Mar 27 11:55:16 2007 +0000
@@ -54,7 +54,8 @@
 	 *   is owned by you.
 	 * @pre IsValidEngine(engine_id).
 	 * @return the VehicleID of the new vehicle, or an invalid VehicleID when
-	 *   it failed. Check the return value using IsValidVehicle.
+	 *   it failed. Check the return value using IsValidVehicle. In test-mode
+	 *   0 is returned if it was successful; any other value indicates failure.
 	 */
 	VehicleID BuildVehicle(TileIndex depot, EngineID engine_id);
 
@@ -66,7 +67,8 @@
 	 * @pre the tile at depot has a depot.
 	 * @pre IsValidVehicle(vehicle_id).
 	 * @return the VehicleID of the new vehicle, or an invalid VehicleID when
-	 *   it failed. Check the return value using IsValidVehicle.
+	 *   it failed. Check the return value using IsValidVehicle. In test-mode
+	 *   0 is returned if it was successful; any other value indicates failure.
 	 */
 	VehicleID CloneVehicle(TileIndex depot, VehicleID vehicle_id, bool share_orders);