An image forming apparatus includes toner-image forming units, an intermediate transfer body, a controller, a detector, an instruction acceptance unit, and a memory. The toner-image forming units form toner images. The toner images are transferred onto the intermediate transfer body. The controller performs control of causing, among the toner-image forming units, one or multiple toner-image forming units to be used to form the toner images to contact the intermediate transfer body, and of separating the other toner-image forming units from the intermediate transfer body. The detector detects a test pattern formed by the toner forming units. The instruction acceptance unit accepts an instruction for performing a detection process with the detector. The memory stores, among forming modes indicating combinations of toner-image forming units to be used, a first forming mode for forming an image and a second forming mode for forming the test pattern.