1. An image forming apparatus comprising: a recorder applying a colorant to a recording medium in accordance with a recording operation of a plurality of recording devices; an image-formation controller instructing the recorder to form a combined image including a plurality of normal images and a test image on the recording medium, the normal image being laid out in a recording area on the recording medium; a reader reading the images formed on the recording medium; a failure detector detecting a recording operation failure of any of the recording devices based on the test image read by the reader; and a determiner determining the quality of each of the normal images based on the detected result of the recording operation failure by the failure detector and positional information on the images in the combined image.