An image forming apparatus has a mode selector that can select a mode of operation in which the image forming apparatus remains online despite an empty printing media container or another error condition. This mode enables a host device to switch from an empty printing media container to a printing media container that is not empty, a feature useful during normal operation, or to continue to issue commands and make settings despite the presence of an error, a feature useful during tests and inspection of the image forming apparatus. Tests and inspection are also facilitated by a mode that simulates the presence of non-installed optional printing media containers, or disables counters and resets error priorities.