Image test apparatus and system for calculating a stack position of a sheet including a defective image

An image test apparatus acquires a result of determination on a defect in a read image obtained by reading an image formed and output on a recording medium, based on a difference between the read image and a test image, acquires a sheet type of a sheet from which the read image is read, calculates a stacked position of a sheet of a defective read image in which the defect is detected among sheets stacked on a discharge tray serving as a discharge destination of the sheet of the read image, on the discharge tray based on the result of the determination on the defect in the read image and based on the acquired sheet type, and controls an indicating unit, which indicates a height at predetermined intervals in a direction in which the sheets are stacked on the discharge tray, based on the calculated stacked position.