Signal processing apparatus and testing method

A signal processing apparatus (10) includes an AD conversion unit (14), a test signal supply unit (12), a determination unit (15), an output unit (16), and an adjustment unit (18). The AD conversion unit (14) converts an analog signal into a digital signal and outputs it. The test signal supply unit (12) adds an offset value to a plurality of predetermined digital data to obtain a test bit pattern, and supplies an analog test signal corresponding to the test bit pattern to the AD conversion unit (14). When the level of the analog test signal supplied to the AD conversion unit (14) has been switched, the determination unit (15) determines whether the value of the bit to be tested of the digital signal converted and output by the AD conversion unit (14) is switched before and after switching of the level of the analog test signal. The output unit (16) outputs the result of determination by the determination unit (15). The adjustment unit (18) adjusts the offset value so that the difference between the test bit